$BKH
BLACK HILLS CORP /SD/ Stock $bkh

$bkh Overview Financials Valuation SEC Filings Company Website

2012 Q4 Form 10-K Financial Statement

#000113046413000071 Filed on February 25, 2013

Income Statement

Concept	2012 Q4	2012	2011 Q4
Revenue	$318.9M	$1.174B	$361.2M
YoY Change	-11.72%	-7.73%	14.66%
Cost Of Revenue
YoY Change
Gross Profit		$766.8M
YoY Change		9.99%
Gross Profit Margin		65.32%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$33.20M	$154.6M	$38.20M
YoY Change	-13.09%	14.04%	0.79%
% of Gross Profit		20.17%
Operating Expenses	$245.4M	$930.2M	$309.0M
YoY Change	-20.58%	-14.34%	22.42%
Operating Profit	$75.26M	$243.7M	$52.14M
YoY Change	44.35%	30.86%	11.27%
Interest Expense	-$26.20M	$113.6M	-$23.20M
YoY Change	12.93%	24.32%	-604.35%
% of Operating Profit	-34.81%	46.62%	-44.5%
Other Income/Expense, Net	$200.0K	$71.00K	$200.0K
YoY Change	0.0%	-91.31%	-71.43%
Pretax Income	$49.30M	$136.9M	$29.10M
YoY Change	69.42%	138.21%	-27.79%
Income Tax	$18.30M	$48.40M	$10.30M
% Of Pretax Income	37.12%	35.36%	35.4%
Net Earnings	$30.77M	$81.53M	$25.59M
YoY Change	20.22%	63.94%	-23.65%
Net Earnings / Revenue	9.65%	6.95%	7.09%
Basic Earnings Per Share	$0.70	$1.86	$0.61
Diluted Earnings Per Share	$0.70	$1.85	$0.60
COMMON SHARES
Basic Shares Outstanding	44.18M shares	43.82M shares	39.47M shares
Diluted Shares Outstanding		44.07M shares

Balance Sheet

Concept	2012 Q4	2012	2011 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$15.50M	$15.50M	$21.60M
YoY Change	-28.24%	-28.24%	31.71%
Cash & Equivalents	$15.46M	$15.50M	$21.63M
Short-Term Investments
Other Short-Term Assets	$28.80M	$148.3M	$21.27M
YoY Change	35.4%	-69.55%	44.72%
Inventory	$77.64M	$77.60M	$84.06M
Prepaid Expenses
Receivables	$163.7M	$163.7M	$156.8M
Other Receivables	$0.00	$0.00	$9.300M
Total Short-Term Assets	$405.1M	$405.1M	$758.9M
YoY Change	-46.62%	-46.62%	10.93%
LONG-TERM ASSETS
Property, Plant & Equipment	$2.743B	$2.743B	$2.790B
YoY Change	-1.68%	-1.68%	11.95%
Goodwill	$353.4M		$353.4M
YoY Change	0.0%		0.0%
Intangibles	$3.620M		$3.843M
YoY Change	-5.8%		-5.55%
Long-Term Investments	$16.40M	$16.40M	$17.30M
YoY Change	-5.2%	-5.2%	-2.81%
Other Assets	$19.42M	$208.2M	$19.94M
YoY Change	-2.61%	2.01%	3.11%
Total Long-Term Assets	$565.2M	$3.324B	$561.3M
YoY Change	0.69%	-1.3%	8.4%
TOTAL ASSETS
Total Short-Term Assets	$405.1M	$405.1M	$758.9M
Total Long-Term Assets	$565.2M	$3.324B	$561.3M
Total Assets	$3.729B	$3.730B	$4.127B
YoY Change	-9.63%	-9.63%	11.2%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$84.42M	$84.40M	$104.7M
YoY Change	-19.4%	-19.39%	-28.53%
Accrued Expenses	$154.4M	$154.4M	$151.3M
YoY Change	2.03%	2.05%	2.49%
Deferred Revenue
YoY Change
Short-Term Debt	$277.0M	$277.0M	$345.0M
YoY Change	-19.71%	-19.71%	38.55%
Long-Term Debt Due	$104.0M	$104.0M	$2.473M
YoY Change	4104.33%	4060.0%	-52.27%
Total Short-Term Liabilities	$734.9M	$734.9M	$878.1M
YoY Change	-16.31%	-16.31%	10.64%
LONG-TERM LIABILITIES
Long-Term Debt	$938.9M	$938.9M	$1.280B
YoY Change	-26.67%	-26.67%	7.96%
Other Long-Term Liabilities	$125.3M	$823.2M	$123.6M
YoY Change	1.41%	8.42%	-3.86%
Total Long-Term Liabilities	$823.2M	$1.762B	$759.3M
YoY Change	8.42%	-13.61%	20.22%
TOTAL LIABILITIES
Total Short-Term Liabilities	$734.9M	$734.9M	$878.1M
Total Long-Term Liabilities	$823.2M	$1.762B	$759.3M
Total Liabilities	$1.558B	$2.497B	$1.637B
YoY Change	-4.84%	-14.42%	14.89%
SHAREHOLDERS EQUITY
Retained Earnings	$492.9M		$476.6M
YoY Change	3.41%		-1.95%
Common Stock	$777.4M		$43.96M
YoY Change	1668.44%		11.91%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$2.245M		$970.0K
YoY Change	131.44%		213.92%
Treasury Stock Shares	71.78K shares		32.77K shares
Shareholders Equity	$1.206B	$1.233B	$1.209B
YoY Change
Total Liabilities & Shareholders Equity	$3.729B	$3.730B	$4.127B
YoY Change	-9.63%	-9.63%	11.2%

Cashflow Statement

Concept	2012 Q4	2012	2011 Q4
OPERATING ACTIVITIES
Net Income	$30.77M	$81.53M	$25.59M
YoY Change	20.22%	63.94%	-23.65%
Depreciation, Depletion And Amortization	$33.20M	$154.6M	$38.20M
YoY Change	-13.09%	14.04%	0.79%
Cash From Operating Activities	$47.30M	$317.0M	$17.20M
YoY Change	175.0%	41.69%	-21.82%
INVESTING ACTIVITIES
Capital Expenditures	-$87.70M	$349.1M	-$114.2M
YoY Change	-23.2%	-20.78%	-23.05%
Acquisitions
YoY Change
Other Investing Activities	$600.0K	$180.0K	-$6.000M
YoY Change	-110.0%	-96.03%	-146.15%
Cash From Investing Activities	-$87.10M	$11.17M	-$120.1M
YoY Change	-27.48%	-102.5%	-11.3%
FINANCING ACTIVITIES
Cash Dividend Paid		$65.26M
YoY Change		10.24%
Common Stock Issuance & Retirement, Net		$4.726M
YoY Change		-96.16%
Debt Paid & Issued, Net		$240.1M
YoY Change		2764.2%
Cash From Financing Activities	-191.9M	-$371.4M	86.90M
YoY Change	-320.83%	-248.8%	0.0%
NET CHANGE
Cash From Operating Activities	47.30M	$317.0M	17.20M
Cash From Investing Activities	-87.10M	$11.17M	-120.1M
Cash From Financing Activities	-191.9M	-$371.4M	86.90M
Net Change In Cash	-231.7M	-$43.31M	-16.00M
YoY Change	1348.12%	-264.47%	-39.62%
FREE CASH FLOW
Cash From Operating Activities	$47.30M	$317.0M	$17.20M
Capital Expenditures	-$87.70M	$349.1M	-$114.2M
Free Cash Flow	$135.0M	-$32.16M	$131.4M
YoY Change	2.74%	-85.18%	-22.89%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2011Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	104748000	USD
CY2012Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	84422000	USD
CY2012Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	163698000	USD
CY2011Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	156774000	USD
CY2010	us-gaap	Accretion Of Discount AccretionOfDiscount	13434000	USD
CY2011	us-gaap	Accretion Of Discount AccretionOfDiscount	19655000	USD
CY2012	us-gaap	Accretion Of Discount AccretionOfDiscount	25509000	USD
CY2011Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	0	USD
CY2012Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	4936000	USD
CY2012Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	154389000	USD
CY2011Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	151319000	USD
CY2011Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	934441000	USD
CY2012Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1188023000	USD
CY2011Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-32878000	USD
CY2012Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-35488000	USD
CY2010Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-23581000	USD
CY2012	us-gaap	Acquisition Costs AcquisitionCosts	55024000	USD
CY2012Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	733095000	USD
CY2011Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	722623000	USD
CY2010	us-gaap	Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation	-33000	USD
CY2012	us-gaap	Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation	117000	USD
CY2011	us-gaap	Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation	-28000	USD
CY2012Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	768000	USD
CY2011Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	1661000	USD
CY2011	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	5655000	USD
CY2012	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	5555000	USD
CY2010	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	5859000	USD
CY2011	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	226000	USD
CY2010	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	240000	USD
CY2012	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	223000	USD
CY2012	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	163000	shares
CY2011	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	141000	shares
CY2010	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	160000	shares
CY2011Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	42914000	USD
CY2012Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	50548000	USD
CY2010Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	42517000	USD
CY2012	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	2568000	USD
CY2011	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	2506000	USD
CY2012	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	5411000	USD
CY2011	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	43000	USD
CY2012	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	1081000	USD
CY2011	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	627000	USD
CY2012	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	736000	USD
CY2011	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-1525000	USD
CY2011Q4	us-gaap	Assets Assets	4127083000	USD
CY2012Q4	us-gaap	Assets Assets	3729471000	USD
CY2011Q4	us-gaap	Assets Current AssetsCurrent	758921000	USD
CY2012Q4	us-gaap	Assets Current AssetsCurrent	405106000	USD
CY2011Q4	us-gaap	Assets Noncurrent AssetsNoncurrent	561326000	USD
CY2012Q4	us-gaap	Assets Noncurrent AssetsNoncurrent	565214000	USD
CY2012Q4	us-gaap	Assets Of Disposal Group Including Discontinued Operation AssetsOfDisposalGroupIncludingDiscontinuedOperation	0	USD
CY2011Q4	us-gaap	Assets Of Disposal Group Including Discontinued Operation AssetsOfDisposalGroupIncludingDiscontinuedOperation	340851000	USD
CY2012	us-gaap	Business Exit Costs BusinessExitCosts	2500000	USD
CY2010	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	48879000	USD
CY2012	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	35556000	USD
CY2011	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	37529000	USD
CY2012Q4	us-gaap	Capitalized Costs Accumulated Depreciation Depletion Amortization And Valuation Allowance For Relating To Oil And Gas Producing Activities CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities	534777000	USD
CY2010Q4	us-gaap	Capitalized Costs Accumulated Depreciation Depletion Amortization And Valuation Allowance For Relating To Oil And Gas Producing Activities CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities	334955000	USD
CY2011Q4	us-gaap	Capitalized Costs Accumulated Depreciation Depletion Amortization And Valuation Allowance For Relating To Oil And Gas Producing Activities CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities	361173000	USD
CY2012	us-gaap	Capitalized Costs Of Unproved Properties Excluded From Amortization CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization	59526000	USD
CY2012Q4	us-gaap	Capitalized Costs Oil And Gas Producing Activities Gross CapitalizedCostsOilAndGasProducingActivitiesGross	721970000	USD
CY2010Q4	us-gaap	Capitalized Costs Oil And Gas Producing Activities Gross CapitalizedCostsOilAndGasProducingActivitiesGross	621138000	USD
CY2011Q4	us-gaap	Capitalized Costs Oil And Gas Producing Activities Gross CapitalizedCostsOilAndGasProducingActivitiesGross	703150000	USD
CY2011Q4	us-gaap	Capitalized Costs Oil And Gas Producing Activities Net CapitalizedCostsOilAndGasProducingActivitiesNet	341977000	USD
CY2010Q4	us-gaap	Capitalized Costs Oil And Gas Producing Activities Net CapitalizedCostsOilAndGasProducingActivitiesNet	286183000	USD
CY2012Q4	us-gaap	Capitalized Costs Oil And Gas Producing Activities Net CapitalizedCostsOilAndGasProducingActivitiesNet	187193000	USD
CY2011Q4	us-gaap	Capitalized Costs Proved Properties CapitalizedCostsProvedProperties	674494000	USD
CY2012Q4	us-gaap	Capitalized Costs Proved Properties CapitalizedCostsProvedProperties	662444000	USD
CY2010Q4	us-gaap	Capitalized Costs Proved Properties CapitalizedCostsProvedProperties	592978000	USD
CY2012Q4	us-gaap	Capitalized Costs Unproved Properties CapitalizedCostsUnprovedProperties	59526000	USD
CY2010Q4	us-gaap	Capitalized Costs Unproved Properties CapitalizedCostsUnprovedProperties	28160000	USD
CY2011Q4	us-gaap	Capitalized Costs Unproved Properties CapitalizedCostsUnprovedProperties	28656000	USD
CY2012Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	15462000	USD
CY2011Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	21628000	USD
CY2010Q4	us-gaap	Cash And Cash Equivalents At Carrying Value Including Discontinued Operations CashAndCashEquivalentsAtCarryingValueIncludingDiscontinuedOperations	32438000	USD
CY2011Q4	us-gaap	Cash And Cash Equivalents At Carrying Value Including Discontinued Operations CashAndCashEquivalentsAtCarryingValueIncludingDiscontinuedOperations	58768000	USD
CY2012Q4	us-gaap	Cash And Cash Equivalents At Carrying Value Including Discontinued Operations CashAndCashEquivalentsAtCarryingValueIncludingDiscontinuedOperations	15462000	USD
CY2009Q4	us-gaap	Cash And Cash Equivalents At Carrying Value Including Discontinued Operations CashAndCashEquivalentsAtCarryingValueIncludingDiscontinuedOperations	112901000	USD
CY2012	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-43306000	USD
CY2010	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-80463000	USD
CY2011	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	26330000	USD
CY2011	us-gaap	Cash Provided By Used In Financing Activities Discontinued Operations CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations	-158000	USD
CY2012	us-gaap	Cash Provided By Used In Financing Activities Discontinued Operations CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations	0	USD
CY2010	us-gaap	Cash Provided By Used In Financing Activities Discontinued Operations CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations	-2037000	USD
CY2011	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	-2359000	USD
CY2010	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	-390000	USD
CY2012	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	-824000	USD
CY2011	us-gaap	Cash Provided By Used In Operating Activities Discontinued Operations CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations	7010000	USD
CY2012	us-gaap	Cash Provided By Used In Operating Activities Discontinued Operations CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations	21184000	USD
CY2010	us-gaap	Cash Provided By Used In Operating Activities Discontinued Operations CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations	-8813000	USD
CY2010	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.44
CY2011	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.46
CY2012	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.48
CY2011Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.365
CY2011Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.365
CY2011Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.365
CY2011Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.365
CY2012Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.370
CY2012Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.370
CY2012Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.370
CY2012Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.370
CY2011Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1.00
CY2012Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1.00
CY2010Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1.00
CY2010Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2012Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2011Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2011Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	100000000	shares
CY2012Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	100000000	shares
CY2010Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	100000000	shares
CY2011Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	43957502	shares
CY2012Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	44278189	shares
CY2010Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	39280048	shares
CY2012Q4	us-gaap	Common Stock Value CommonStockValue	44278000	USD
CY2011Q4	us-gaap	Common Stock Value CommonStockValue	43958000	USD
CY2011	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	40433000	USD
CY2010	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	64268000	USD
CY2012	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	78918000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	147153000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards State And Local DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal	8300000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards State And Local DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal	12311000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	17683000	USD
CY2012	us-gaap	Costs And Expenses CostsAndExpenses	370736000	USD
CY2011	us-gaap	Costs And Expenses CostsAndExpenses	375369000	USD
CY2010	us-gaap	Costs And Expenses CostsAndExpenses	351619000	USD
CY2010	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	678000	USD
CY2012	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	4972000	USD
CY2011	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-14539000	USD
CY2010	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	4815000	USD
CY2012	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	8684000	USD
CY2011	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	-15376000	USD
CY2010	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	4137000	USD
CY2011	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	-837000	USD
CY2012	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	3712000	USD
CY2010	us-gaap	Decrease Due To Sales Of Minerals In Place DecreaseDueToSalesOfMineralsInPlace	738000	USD
CY2011	us-gaap	Decrease Due To Sales Of Minerals In Place DecreaseDueToSalesOfMineralsInPlace	1013000	USD
CY2012	us-gaap	Decrease Due To Sales Of Minerals In Place DecreaseDueToSalesOfMineralsInPlace	37175000	USD
CY2010	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	20186000	USD
CY2012	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	39876000	USD
CY2011	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	30876000	USD
CY2011	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	33600000	USD
CY2010	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	17354000	USD
CY2012	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	39716000	USD
CY2011Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	677106000	USD
CY2012Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	694880000	USD
CY2012	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	68000	USD
CY2011	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	2970000	USD
CY2010	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-2495000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Derivative Instruments DeferredTaxAssetsDerivativeInstruments	39099000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Derivative Instruments DeferredTaxAssetsDerivativeInstruments	35947000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	386203000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	413320000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Net Current DeferredTaxAssetsNetCurrent	77231000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Net Current DeferredTaxAssetsNetCurrent	37202000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	195834000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	40642000	USD
CY2012Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	15546000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	25101000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Other Comprehensive Loss DeferredTaxAssetsOtherComprehensiveLoss	36398000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Other Comprehensive Loss DeferredTaxAssetsOtherComprehensiveLoss	20038000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	57471000	USD
CY2011Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	0	USD
CY2011Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	22488000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	23767000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	2605000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	3101000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Impairment Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses	55971000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Impairment Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses	47033000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	6192000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	773000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	308677000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	263786000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Deferred Expense DeferredTaxLiabilitiesDeferredExpense	17723000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Deferred Expense DeferredTaxLiabilitiesDeferredExpense	15663000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	385908000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	300988000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	20739000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	13961000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	571262000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	508261000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Regulatory Assets DeferredTaxLiabilitiesRegulatoryAssets	23537000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Regulatory Assets DeferredTaxLiabilitiesRegulatoryAssets	23498000	USD
CY2011	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0875
CY2012	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0725
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Decrease On Accumulated Postretirement Benefit Obligation1 DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1	1771000	USD
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Decrease On Service And Interest Cost Components1 DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1	107000	USD
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Increase On Accumulated Postretirement Benefit Obligation DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation	2082000	USD
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Increase On Service And Interest Cost Components DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents	127000	USD
CY2012	us-gaap	Defined Benefit Plan Measurement Date DefinedBenefitPlanMeasurementDate	December 31
CY2012	us-gaap	Defined Benefit Plan Target Plan Asset Allocations DefinedBenefitPlanTargetPlanAssetAllocations	1
CY2011	us-gaap	Defined Benefit Plan Target Plan Asset Allocations DefinedBenefitPlanTargetPlanAssetAllocations	1
CY2012	us-gaap	Defined Contribution Plan Maximum Annual Contribution Per Employee Percent DefinedContributionPlanMaximumAnnualContributionPerEmployeePercent	0.50
CY2010	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	126606000	USD
CY2012	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	154632000	USD
CY2011	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	135591000	USD
CY2011Q4	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	18583000	USD
CY2012Q4	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	3236000	USD
CY2012Q4	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	510000	USD
CY2011Q4	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	1971000	USD
CY2010	us-gaap	Derivative Instruments Gain Loss Recognized In Income Net DerivativeInstrumentsGainLossRecognizedInIncomeNet	-28505000	USD
CY2012	us-gaap	Derivative Instruments Gain Loss Recognized In Income Net DerivativeInstrumentsGainLossRecognizedInIncomeNet	-11077000	USD
CY2011	us-gaap	Derivative Instruments Gain Loss Recognized In Income Net DerivativeInstrumentsGainLossRecognizedInIncomeNet	-55383000	USD
CY2012	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	1882000	USD
CY2011	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	-42010000	USD
CY2010	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	-15193000	USD
CY2012Q4	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	96541000	USD
CY2011Q4	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	84367000	USD
CY2012Q4	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	16941000	USD
CY2011Q4	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	49033000	USD
CY2010	us-gaap	Dilutive Securities DilutiveSecurities	-288000	USD
CY2010	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves10 Percent Annual Discount For Estimated Timing Of Cash Flows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves10PercentAnnualDiscountForEstimatedTimingOfCashFlows	154551000	USD
CY2011	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves10 Percent Annual Discount For Estimated Timing Of Cash Flows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves10PercentAnnualDiscountForEstimatedTimingOfCashFlows	197215000	USD
CY2012	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves10 Percent Annual Discount For Estimated Timing Of Cash Flows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves10PercentAnnualDiscountForEstimatedTimingOfCashFlows	101632000	USD
CY2010	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Cash Inflows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureCashInflows	764585000	USD
CY2012	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Cash Inflows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureCashInflows	502769000	USD
CY2011	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Cash Inflows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureCashInflows	931637000	USD
CY2012	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Development Costs DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureDevelopmentCosts	8462000	USD
CY2011	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Development Costs DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureDevelopmentCosts	92233000	USD
CY2010	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Development Costs DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureDevelopmentCosts	73805000	USD
CY2010	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Income Tax Expense DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureIncomeTaxExpense	111666000	USD
CY2011	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Income Tax Expense DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureIncomeTaxExpense	157922000	USD
CY2012	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Income Tax Expense DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureIncomeTaxExpense	69877000	USD
CY2011	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Net Cash Flows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureNetCashFlows	400572000	USD
CY2012	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Net Cash Flows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureNetCashFlows	237735000	USD
CY2010	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Net Cash Flows DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureNetCashFlows	322659000	USD
CY2012	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Production Costs DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureProductionCosts	186695000	USD
CY2011	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Production Costs DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureProductionCosts	280910000	USD
CY2010	us-gaap	Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves Future Production Costs DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureProductionCosts	256455000	USD
CY2012	us-gaap	Disposal Date1 DisposalDate1	2012-02-29
CY2009Q4	us-gaap	Disposal Group Including Discontinued Operation Cash And Cash Equivalents DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents	97500000	USD
CY2010Q4	us-gaap	Disposal Group Including Discontinued Operation Cash And Cash Equivalents DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents	16000000	USD
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Tax Contingencies EffectiveIncomeTaxRateReconciliationTaxContingencies	0.008
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.000
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	-0.032
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.000
CY2012Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	7800000	USD
CY2012	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y11M
CY2012	us-gaap	Exploration Costs ExplorationCosts	328000	USD
CY2010	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.011
CY2011	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.018
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Tax Contingencies EffectiveIncomeTaxRateReconciliationTaxContingencies	0.012
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Tax Contingencies EffectiveIncomeTaxRateReconciliationTaxContingencies	0.028
CY2011Q4	us-gaap	Disposal Group Including Discontinued Operation Cash And Cash Equivalents DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents	37100000	USD
CY2012	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	65262000	USD
CY2011	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	59202000	USD
CY2010	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	56467000	USD
CY2012	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.86
CY2010	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.76
CY2011	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.25
CY2011Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.69
CY2011Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.20
CY2011Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.27
CY2011Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.61
CY2012Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.79
CY2012Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.68
CY2012Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.70
CY2012Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.31
CY2011	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
CY2012	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.85
CY2010	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.76
CY2011Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.60
CY2011Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.19
CY2011Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.68
CY2011Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.27
CY2012Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.31
CY2012Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.70
CY2012Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.68
CY2012Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.78
CY2010	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.260
CY2012	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.354
CY2011	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.311
CY2010	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2011	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2012	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depletion EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepletion	-0.017
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depletion EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepletion	-0.013
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depletion EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepletion	-0.025
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.005
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.004
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.004
CY2012	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.020
CY2012	us-gaap	Extensions Discoveries Additions And Improved Recovery Less Related Costs ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts	19870000	USD
CY2010	us-gaap	Extensions Discoveries Additions And Improved Recovery Less Related Costs ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts	17076000	USD
CY2011	us-gaap	Extensions Discoveries Additions And Improved Recovery Less Related Costs ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts	31179000	USD
CY2012Q4	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0	USD
CY2011Q4	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0	USD
CY2012Q4	us-gaap	Fair Value Assets Level2 To Level1 Transfers Amount FairValueAssetsLevel2ToLevel1TransfersAmount	0	USD
CY2011Q4	us-gaap	Fair Value Assets Level2 To Level1 Transfers Amount FairValueAssetsLevel2ToLevel1TransfersAmount	0	USD
CY2012	us-gaap	Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss Included In Investment Income FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLossIncludedInInvestmentIncome	-54000	USD
CY2012Q4	us-gaap	Fair Value Liabilities Level1 To Level2 Transfers Amount FairValueLiabilitiesLevel1ToLevel2TransfersAmount	0	USD
CY2011Q4	us-gaap	Fair Value Liabilities Level1 To Level2 Transfers Amount FairValueLiabilitiesLevel1ToLevel2TransfersAmount	0	USD
CY2012Q4	us-gaap	Fair Value Liabilities Level2 To Level1 Transfers Amount FairValueLiabilitiesLevel2ToLevel1TransfersAmount	0	USD
CY2011Q4	us-gaap	Fair Value Liabilities Level2 To Level1 Transfers Amount FairValueLiabilitiesLevel2ToLevel1TransfersAmount	0	USD
CY2012	us-gaap	Fair Value Liabilities Measured On Recurring Basis Change In Unrealized Gain Loss Included In Other Income FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLossIncludedInOtherIncome	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Liability Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersIntoLevel3	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Liability Transfers Out Of Level3 FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3	1347000	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings1 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Other Comprehensive Income Loss FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss	414000	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Issues FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases	192000	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements	4000	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Out Of Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3	499000	USD
CY2011Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	768000	USD
CY2012Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	43000	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Included In Earnings FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Included In Other Comprehensive Income FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome	182000	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Issues FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases	0	USD
CY2012	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements	0	USD
CY2011Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	1165000	USD
CY2012Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	0	USD
CY2012	us-gaap	Finite Lived Intangible Asset Useful Life FiniteLivedIntangibleAssetUsefulLife	P20Y
CY2012Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	200000	USD
CY2012Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	200000	USD
CY2012Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	200000	USD
CY2012Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	200000	USD
CY2012Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	200000	USD
CY2012	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	29129000	USD
CY2011	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	0	USD
CY2010	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	8921000	USD
CY2012	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	29129000	USD
CY2010	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	8921000	USD
CY2011	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	0	USD
CY2012Q4	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	1800000	USD
CY2012Q3	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	27300000	USD
CY2011Q4	us-gaap	Goodwill Goodwill	353396000	USD
CY2012Q4	us-gaap	Goodwill Goodwill	353396000	USD
CY2010Q4	us-gaap	Goodwill Goodwill	353396000	USD
CY2011	us-gaap	Goodwill Other Changes GoodwillOtherChanges	0	USD
CY2012	us-gaap	Goodwill Other Changes GoodwillOtherChanges	0	USD
CY2012	us-gaap	Gross Profit GrossProfit	766818000	USD
CY2011	us-gaap	Gross Profit GrossProfit	697199000	USD
CY2010	us-gaap	Gross Profit GrossProfit	652724000	USD
CY2012Q4	us-gaap	Guarantee Obligations Maximum Exposure GuaranteeObligationsMaximumExposure	175273000	USD
CY2012	us-gaap	Impairment Of Oil And Gas Properties ImpairmentOfOilAndGasProperties	26868000	USD
CY2011	us-gaap	Impairment Of Oil And Gas Properties ImpairmentOfOilAndGasProperties	0	USD
CY2010	us-gaap	Impairment Of Oil And Gas Properties ImpairmentOfOilAndGasProperties	0	USD
CY2012Q2	us-gaap	Impairment Of Oil And Gas Properties ImpairmentOfOilAndGasProperties	26900000	USD
CY2010	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	63141000	USD
CY2011	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	40365000	USD
CY2012	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	88505000	USD
CY2011	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	57468000	USD
CY2012	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	136895000	USD
CY2010	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	83751000	USD
CY2010	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	63141000	USD
CY2011	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	40365000	USD
CY2012	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	88505000	USD
CY2011Q3	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	-11163000	USD
CY2011Q4	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	18754000	USD
CY2011Q2	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	3706000	USD
CY2011Q1	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	29068000	USD
CY2012Q4	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	30934000	USD
CY2012Q3	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	34623000	USD
CY2012Q1	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	35271000	USD
CY2012Q2	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	-12323000	USD
CY2010	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.62
CY2012	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	2.02
CY2011	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.01
CY2011Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-0.29
CY2011Q4	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.45
CY2011Q1	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.74
CY2011Q2	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.09
CY2012Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.79
CY2012Q2	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-0.28
CY2012Q1	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.81
CY2012Q4	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.70
CY2012	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	2.01
CY2011	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.01
CY2010	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.62
CY2011Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-0.29
CY2011Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.44
CY2011Q1	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.73
CY2011Q2	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.09
CY2012Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.70
CY2012Q2	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-0.28
CY2012Q1	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.80
CY2012Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.78
CY2011	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	9365000	USD
CY2010	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	5544000	USD
CY2012	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	-6977000	USD
CY2011Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	6839000	USD
CY2011Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	638000	USD
CY2011Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-2158000	USD
CY2011Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	4046000	USD
CY2012Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-1160000	USD
CY2012Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-167000	USD
CY2012Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-5484000	USD
CY2012Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-166000	USD
CY2011	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.24
CY2010	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.14
CY2012	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.16
CY2011Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.05
CY2011Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.02
CY2011Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.11
CY2011Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.16
CY2012Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.13
CY2012Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.03
CY2012Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.00
CY2012Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.00
CY2010	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.14
CY2012	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.16
CY2011	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.23
CY2011Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.05
CY2011Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.02
CY2011Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.10
CY2011Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.16
CY2012Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.00
CY2012Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.03
CY2012Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.00
CY2012Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.12
CY2012	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	10000	USD
CY2010	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	1559000	USD
CY2011	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	1121000	USD
CY2011	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	18224000	USD
CY2012	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	48400000	USD
CY2010	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	22169000	USD
CY2010	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-9384000	USD
CY2012	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	3027000	USD
CY2011	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-9854000	USD
CY2011Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	9344000	USD
CY2012Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	0	USD
CY2011	us-gaap	Increase Decrease In Estimated Future Development Costs IncreaseDecreaseInEstimatedFutureDevelopmentCosts	43809000	USD
CY2010	us-gaap	Increase Decrease In Estimated Future Development Costs IncreaseDecreaseInEstimatedFutureDevelopmentCosts	-17125000	USD
CY2012	us-gaap	Increase Decrease In Estimated Future Development Costs IncreaseDecreaseInEstimatedFutureDevelopmentCosts	43854000	USD
CY2010	us-gaap	Increase Decrease In Fair Value Of Unhedged Derivative Instruments IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstruments	-15193000	USD
CY2011	us-gaap	Increase Decrease In Fair Value Of Unhedged Derivative Instruments IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstruments	-42010000	USD
CY2012	us-gaap	Increase Decrease In Fair Value Of Unhedged Derivative Instruments IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstruments	1882000	USD
CY2012	us-gaap	Increase Decrease In Future Income Tax Expense Estimates On Future Cash Flows Related To Proved Oil And Gas Reserves IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves	36578000	USD
CY2011	us-gaap	Increase Decrease In Future Income Tax Expense Estimates On Future Cash Flows Related To Proved Oil And Gas Reserves IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves	-23283000	USD
CY2010	us-gaap	Increase Decrease In Future Income Tax Expense Estimates On Future Cash Flows Related To Proved Oil And Gas Reserves IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves	-23233000	USD
CY2012	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-6343000	USD
CY2011	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	21385000	USD
CY2010	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	338000	USD
CY2010	us-gaap	Increase Decrease In Other Accounts Payable And Accrued Liabilities IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities	-12848000	USD
CY2011	us-gaap	Increase Decrease In Other Accounts Payable And Accrued Liabilities IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities	-31091000	USD
CY2012	us-gaap	Increase Decrease In Other Accounts Payable And Accrued Liabilities IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities	-10713000	USD
CY2011	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	11118000	USD
CY2012	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	6732000	USD
CY2010	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	1013000	USD
CY2010	us-gaap	Increase Decrease In Other Regulatory Assets IncreaseDecreaseInOtherRegulatoryAssets	21283000	USD
CY2012	us-gaap	Increase Decrease In Other Regulatory Assets IncreaseDecreaseInOtherRegulatoryAssets	-12864000	USD
CY2011	us-gaap	Increase Decrease In Other Regulatory Assets IncreaseDecreaseInOtherRegulatoryAssets	-12691000	USD
CY2010	us-gaap	Increase Decrease In Regulatory Liabilities IncreaseDecreaseInRegulatoryLiabilities	50000	USD
CY2011	us-gaap	Increase Decrease In Regulatory Liabilities IncreaseDecreaseInRegulatoryLiabilities	11198000	USD
CY2012	us-gaap	Increase Decrease In Regulatory Liabilities IncreaseDecreaseInRegulatoryLiabilities	3194000	USD
CY2010	us-gaap	Increase Due To Purchases Of Minerals In Place IncreaseDueToPurchasesOfMineralsInPlace	0	USD
CY2011	us-gaap	Increase Due To Purchases Of Minerals In Place IncreaseDueToPurchasesOfMineralsInPlace	0	USD
CY2012	us-gaap	Increase Due To Purchases Of Minerals In Place IncreaseDueToPurchasesOfMineralsInPlace	0	USD
CY2011Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	3843000	USD
CY2012Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	3620000	USD
CY2010Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	4069000	USD
CY2012Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	3729471000	USD
CY2011Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	4127083000	USD
CY2009Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	4309000	USD
CY2011	us-gaap	Interest Costs Incurred InterestCostsIncurred	116684000	USD
CY2012	us-gaap	Interest Costs Incurred InterestCostsIncurred	117754000	USD
CY2010	us-gaap	Interest Costs Incurred InterestCostsIncurred	105676000	USD
CY2012	us-gaap	Interest Expense InterestExpense	113610000	USD
CY2011	us-gaap	Interest Expense InterestExpense	91383000	USD
CY2010	us-gaap	Interest Expense InterestExpense	90606000	USD
CY2012	us-gaap	Interest Paid Net InterestPaidNet	116593000	USD
CY2010	us-gaap	Interest Paid Net InterestPaidNet	101947000	USD
CY2011	us-gaap	Interest Paid Net InterestPaidNet	103110000	USD
CY2011Q4	us-gaap	Inventory Net InventoryNet	84064000	USD
CY2012Q4	us-gaap	Inventory Net InventoryNet	77643000	USD
CY2011Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	40838000	USD
CY2012Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	43397000	USD
CY2010	us-gaap	Investment Income Interest InvestmentIncomeInterest	541000	USD
CY2011	us-gaap	Investment Income Interest InvestmentIncomeInterest	2017000	USD
CY2012	us-gaap	Investment Income Interest InvestmentIncomeInterest	1957000	USD
CY2012	us-gaap	Investment Tax Credit InvestmentTaxCredit	-228000	USD
CY2010	us-gaap	Investment Tax Credit InvestmentTaxCredit	-337000	USD
CY2011	us-gaap	Investment Tax Credit InvestmentTaxCredit	-246000	USD
CY2010	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	4219000	USD
CY2011	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	6125000	USD
CY2012	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	6839000	USD
CY2011Q4	us-gaap	Letters Of Credit Outstanding Amount LettersOfCreditOutstandingAmount	43700000	USD
CY2012Q4	us-gaap	Letters Of Credit Outstanding Amount LettersOfCreditOutstandingAmount	36300000	USD
CY2012Q4	us-gaap	Liabilities Current LiabilitiesCurrent	734889000	USD
CY2011Q4	us-gaap	Liabilities Current LiabilitiesCurrent	878067000	USD
CY2011Q4	us-gaap	Liabilities Noncurrent LiabilitiesNoncurrent	759271000	USD
CY2012Q4	us-gaap	Liabilities Noncurrent LiabilitiesNoncurrent	823196000	USD
CY2012Q4	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation	0	USD
CY2011Q4	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation	173929000	USD
CY2009Q4	us-gaap	Liability For Uncertain Tax Positions Noncurrent LiabilityForUncertainTaxPositionsNoncurrent	107088000	USD
CY2011Q4	us-gaap	Liability For Uncertain Tax Positions Noncurrent LiabilityForUncertainTaxPositionsNoncurrent	49327000	USD
CY2010Q4	us-gaap	Liability For Uncertain Tax Positions Noncurrent LiabilityForUncertainTaxPositionsNoncurrent	50135000	USD
CY2012Q4	us-gaap	Liability For Uncertain Tax Positions Noncurrent LiabilityForUncertainTaxPositionsNoncurrent	40683000	USD
CY2012	us-gaap	Line Of Credit Facility Expiration Date1 LineOfCreditFacilityExpirationDate1	2017-02-01
CY2012Q4	us-gaap	Long Term Debt LongTermDebt	1042850000	USD
CY2011Q4	us-gaap	Long Term Debt LongTermDebt	1282882000	USD
CY2011Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	2473000	USD
CY2012Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	103973000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	597055000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	103973000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	0	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	78947000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	6963000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	256023000	USD
CY2012Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	938877000	USD
CY2011Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	1280409000	USD
CY2012Q4	us-gaap	Long Term Investments LongTermInvestments	16402000	USD
CY2011Q4	us-gaap	Long Term Investments LongTermInvestments	17261000	USD
CY2010	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	160953000	USD
CY2011	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	249633000	USD
CY2012	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-371446000	USD
CY2011	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	249791000	USD
CY2012	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	-371446000	USD
CY2010	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	162990000	USD
CY2010	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-389168000	USD
CY2012	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	11169000	USD
CY2011	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-447007000	USD
CY2010	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-388778000	USD
CY2011	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-444648000	USD
CY2012	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-95518000	USD
CY2011	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	223704000	USD
CY2010	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	147752000	USD
CY2012	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	316971000	USD
CY2012	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	295787000	USD
CY2011	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	216694000	USD
CY2010	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	156565000	USD
CY2012	us-gaap	Net Income Loss NetIncomeLoss	81528000	USD
CY2011	us-gaap	Net Income Loss NetIncomeLoss	49730000	USD
CY2010	us-gaap	Net Income Loss NetIncomeLoss	68685000	USD
CY2011	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	49730000	USD
CY2010	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	68685000	USD
CY2012	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	81528000	USD
CY2010	us-gaap	Net Increase Decrease In Sales And Transfer Prices And Production Costs NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts	57380000	USD
CY2012	us-gaap	Net Increase Decrease In Sales And Transfer Prices And Production Costs NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts	-42639000	USD
CY2011	us-gaap	Net Increase Decrease In Sales And Transfer Prices And Production Costs NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts	57087000	USD
CY2012	us-gaap	Operating Expenses OperatingExpenses	930173000	USD
CY2010	us-gaap	Operating Expenses OperatingExpenses	1036271000	USD
CY2011	us-gaap	Operating Expenses OperatingExpenses	1085949000	USD
CY2011	us-gaap	Operating Income Loss OperatingIncomeLoss	186239000	USD
CY2010	us-gaap	Operating Income Loss OperatingIncomeLoss	183420000	USD
CY2012	us-gaap	Operating Income Loss OperatingIncomeLoss	243711000	USD
CY2011Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	52140000	USD
CY2011Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	36160000	USD
CY2011Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	39572000	USD
CY2011Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	58367000	USD
CY2012Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	77810000	USD
CY2012Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	20591000	USD
CY2012Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	70048000	USD
CY2012Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	75262000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	2690000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	1269000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	1465000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	2144000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	2377000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	2811000	USD
CY2011Q4	us-gaap	Other Assets Current OtherAssetsCurrent	21266000	USD
CY2012Q4	us-gaap	Other Assets Current OtherAssetsCurrent	28795000	USD
CY2012Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	19420000	USD
CY2011Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	19941000	USD
CY2012	us-gaap	Other Comprehensive Income Amortization Of Defined Benefit Plan Net Prior Service Cost Recognized In Net Periodic Pension Cost Tax OtherComprehensiveIncomeAmortizationOfDefinedBenefitPlanNetPriorServiceCostRecognizedInNetPeriodicPensionCostTax	86000	USD
CY2011	us-gaap	Other Comprehensive Income Amortization Of Defined Benefit Plan Net Prior Service Cost Recognized In Net Periodic Pension Cost Tax OtherComprehensiveIncomeAmortizationOfDefinedBenefitPlanNetPriorServiceCostRecognizedInNetPeriodicPensionCostTax	176000	USD
CY2010	us-gaap	Other Comprehensive Income Amortization Of Defined Benefit Plan Net Prior Service Cost Recognized In Net Periodic Pension Cost Tax OtherComprehensiveIncomeAmortizationOfDefinedBenefitPlanNetPriorServiceCostRecognizedInNetPeriodicPensionCostTax	111000	USD
CY2010	us-gaap	Other Comprehensive Income Defined Benefit Plan Net Prior Service Costs Credit Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax	214000	USD
CY2011	us-gaap	Other Comprehensive Income Defined Benefit Plan Net Prior Service Costs Credit Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax	325000	USD
CY2012	us-gaap	Other Comprehensive Income Defined Benefit Plan Net Prior Service Costs Credit Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax	157000	USD
CY2011	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-7609000	USD
CY2012	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-542000	USD
CY2010	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-1307000	USD
CY2012	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-296000	USD
CY2011	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-4135000	USD
CY2010	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-674000	USD
CY2011	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-9297000	USD
CY2012	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-2610000	USD
CY2010	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-4417000	USD
CY2010	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	64268000	USD
CY2012	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	78918000	USD
CY2011	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	40433000	USD
CY2011	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment On Derivatives Included In Net Income Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentOnDerivativesIncludedInNetIncomeNetOfTax	1468000	USD
CY2012	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment On Derivatives Included In Net Income Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentOnDerivativesIncludedInNetIncomeNetOfTax	-643000	USD
CY2010	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment On Derivatives Included In Net Income Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentOnDerivativesIncludedInNetIncomeNetOfTax	-4232000	USD
CY2010	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment On Derivatives Included In Net Income Tax OtherComprehensiveIncomeLossReclassificationAdjustmentOnDerivativesIncludedInNetIncomeTax	-2498000	USD
CY2012	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment On Derivatives Included In Net Income Tax OtherComprehensiveIncomeLossReclassificationAdjustmentOnDerivativesIncludedInNetIncomeTax	-534000	USD
CY2011	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment On Derivatives Included In Net Income Tax OtherComprehensiveIncomeLossReclassificationAdjustmentOnDerivativesIncludedInNetIncomeTax	709000	USD
CY2010	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax	1336000	USD
CY2011	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax	-2831000	USD
CY2012	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax	-1268000	USD
CY2010	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	636000	USD
CY2012	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	-887000	USD
CY2011	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	-1708000	USD
CY2010	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	980000	USD
CY2012	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	2052000	USD
CY2011	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	710000	USD
CY2012	us-gaap	Other Expenses OtherExpenses	71000	USD
CY2011	us-gaap	Other Expenses OtherExpenses	817000	USD
CY2010	us-gaap	Other Expenses OtherExpenses	140000	USD
CY2010	us-gaap	Other Income OtherIncome	2733000	USD
CY2011	us-gaap	Other Income OtherIncome	2490000	USD
CY2012	us-gaap	Other Income OtherIncome	2486000	USD
CY2012Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	125294000	USD
CY2011Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	123553000	USD
CY2011	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-4947000	USD
CY2010	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	9710000	USD
CY2012	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-2751000	USD
CY2012	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	2965000	USD
CY2011	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	3726000	USD
CY2010	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	7148000	USD
CY2012Q4	us-gaap	Other Tax Carryforward Gross Amount OtherTaxCarryforwardGrossAmount	2300000	USD
CY2011	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	4533000	USD
CY2010	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-15407000	USD
CY2012	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	180000	USD
CY2012	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	349129000	USD
CY2010	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	472292000	USD
CY2011	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	440698000	USD
CY2010	us-gaap	Payments Of Dividends PaymentsOfDividends	56467000	USD
CY2012	us-gaap	Payments Of Dividends PaymentsOfDividends	65262000	USD
CY2011	us-gaap	Payments Of Dividends PaymentsOfDividends	59202000	USD
CY2010	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	2250000	USD
CY2011	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	0	USD
CY2012	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	0	USD
CY2012	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	20973000	USD
CY2011	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	14586000	USD
CY2010	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	16342000	USD
CY2011Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	177480000	USD
CY2012Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	167397000	USD
CY2011	us-gaap	Pension Contributions PensionContributions	11050000	USD
CY2012	us-gaap	Pension Contributions PensionContributions	25350000	USD
CY2010	us-gaap	Pension Contributions PensionContributions	30015000	USD
CY2012	us-gaap	Previously Estimated Development Costs Incurred During Period PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod	-21931000	USD
CY2010	us-gaap	Previously Estimated Development Costs Incurred During Period PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod	-4975000	USD
CY2011	us-gaap	Previously Estimated Development Costs Incurred During Period PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod	-18940000	USD
CY2012	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	107511000	USD
CY2010	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	0	USD
CY2011	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	0	USD
CY2010	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	3246000	USD
CY2011	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	123041000	USD
CY2012	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	4726000	USD
CY2010	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	200000000	USD
CY2012	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
CY2011	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
CY2011	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	1017300000	USD
CY2012	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	203753000	USD
CY2010	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	854500000	USD
CY2011	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1666000	USD
CY2012	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-2833000	USD
CY2010	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-8363000	USD
CY2010	us-gaap	Proceeds From Sale Of Other Property Plant And Equipment ProceedsFromSaleOfOtherPropertyPlantAndEquipment	70357000	USD
CY2011	us-gaap	Proceeds From Sale Of Other Property Plant And Equipment ProceedsFromSaleOfOtherPropertyPlantAndEquipment	583000	USD
CY2012	us-gaap	Proceeds From Sale Of Other Property Plant And Equipment ProceedsFromSaleOfOtherPropertyPlantAndEquipment	253791000	USD
CY2010	us-gaap	Profit Loss ProfitLoss	68685000	USD
CY2012	us-gaap	Profit Loss ProfitLoss	81528000	USD
CY2011	us-gaap	Profit Loss ProfitLoss	49730000	USD
CY2011Q4	us-gaap	Profit Loss ProfitLoss	25593000	USD
CY2011Q2	us-gaap	Profit Loss ProfitLoss	7752000	USD
CY2011Q3	us-gaap	Profit Loss ProfitLoss	-10525000	USD
CY2011Q1	us-gaap	Profit Loss ProfitLoss	26910000	USD
CY2012Q1	us-gaap	Profit Loss ProfitLoss	29787000	USD
CY2012Q3	us-gaap	Profit Loss ProfitLoss	34457000	USD
CY2012Q2	us-gaap	Profit Loss ProfitLoss	-13483000	USD
CY2012Q4	us-gaap	Profit Loss ProfitLoss	30767000	USD
CY2011Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3724016000	USD
CY2012Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3930772000	USD
CY2011	us-gaap	Property Plant And Equipment Gross Period Increase Decrease PropertyPlantAndEquipmentGrossPeriodIncreaseDecrease	431707000	USD
CY2012	us-gaap	Property Plant And Equipment Gross Period Increase Decrease PropertyPlantAndEquipmentGrossPeriodIncreaseDecrease	347980000	USD
CY2012Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2742749000	USD
CY2011Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2789575000	USD
CY2012	us-gaap	Property Plant And Equipment Preproduction Design And Development Costs PropertyPlantAndEquipmentPreproductionDesignAndDevelopmentCosts	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-weight:bold;">Development Costs</font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">According to accounting standards for business combinations, we expense, when incurred, development and acquisition costs associated with corporate development activities prior to acquiring or beginning construction of a project. Expensed development costs are included in Other operating expenses on the accompanying Consolidated Statements of Income.</font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></div>
CY2011	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	932000	USD
CY2010	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	2996000	USD
CY2012	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	540000	USD
CY2011Q4	us-gaap	Regulatory Assets RegulatoryAssets	242130000	USD
CY2012Q4	us-gaap	Regulatory Assets RegulatoryAssets	219393000	USD
CY2012Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	31125000	USD
CY2011Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	59955000	USD
CY2011Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	182175000	USD
CY2012Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	188268000	USD
CY2011Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	124448000	USD
CY2012Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	141284000	USD
CY2011Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	16231000	USD
CY2012Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	13628000	USD
CY2012Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	127656000	USD
CY2011Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	108217000	USD
CY2012	us-gaap	Repayments Of Lines Of Credit RepaymentsOfLinesOfCredit	271753000	USD
CY2010	us-gaap	Repayments Of Lines Of Credit RepaymentsOfLinesOfCredit	770000000	USD
CY2011	us-gaap	Repayments Of Lines Of Credit RepaymentsOfLinesOfCredit	821300000	USD
CY2012	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	240077000	USD
CY2011	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	8382000	USD
CY2010	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	59926000	USD
CY2012Q4	us-gaap	Restricted Cash And Investments Current RestrictedCashAndInvestmentsCurrent	7916000	USD
CY2011Q4	us-gaap	Restricted Cash And Investments Current RestrictedCashAndInvestmentsCurrent	9254000	USD
CY2011	us-gaap	Results Of Operations Depreciation Depletion And Amortization And Valuation Provisions ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions	34415000	USD
CY2010	us-gaap	Results Of Operations Depreciation Depletion And Amortization And Valuation Provisions ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions	29013000	USD
CY2012	us-gaap	Results Of Operations Depreciation Depletion And Amortization And Valuation Provisions ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions	37323000	USD
CY2012	us-gaap	Results Of Operations Expense From Oil And Gas Producing Activities ResultsOfOperationsExpenseFromOilAndGasProducingActivities	58545000	USD
CY2010	us-gaap	Results Of Operations Expense From Oil And Gas Producing Activities ResultsOfOperationsExpenseFromOilAndGasProducingActivities	50935000	USD
CY2011	us-gaap	Results Of Operations Expense From Oil And Gas Producing Activities ResultsOfOperationsExpenseFromOilAndGasProducingActivities	58235000	USD
CY2012	us-gaap	Results Of Operations Impairment Of Oil And Gas Properties ResultsOfOperationsImpairmentOfOilAndGasProperties	26868000	USD
CY2011	us-gaap	Results Of Operations Impairment Of Oil And Gas Properties ResultsOfOperationsImpairmentOfOilAndGasProperties	0	USD
CY2010	us-gaap	Results Of Operations Impairment Of Oil And Gas Properties ResultsOfOperationsImpairmentOfOilAndGasProperties	0	USD
CY2011	us-gaap	Results Of Operations Income Before Income Taxes ResultsOfOperationsIncomeBeforeIncomeTaxes	21573000	USD
CY2012	us-gaap	Results Of Operations Income Before Income Taxes ResultsOfOperationsIncomeBeforeIncomeTaxes	20527000	USD
CY2010	us-gaap	Results Of Operations Income Before Income Taxes ResultsOfOperationsIncomeBeforeIncomeTaxes	23229000	USD
CY2011	us-gaap	Results Of Operations Income Tax Expense ResultsOfOperationsIncomeTaxExpense	7442000	USD
CY2012	us-gaap	Results Of Operations Income Tax Expense ResultsOfOperationsIncomeTaxExpense	7082000	USD
CY2010	us-gaap	Results Of Operations Income Tax Expense ResultsOfOperationsIncomeTaxExpense	8014000	USD
CY2010	us-gaap	Results Of Operations Oil And Gas Producing Activities Net Income Excluding Corporate Overhead And Interest Costs ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts	15215000	USD
CY2012	us-gaap	Results Of Operations Oil And Gas Producing Activities Net Income Excluding Corporate Overhead And Interest Costs ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts	13445000	USD
CY2011	us-gaap	Results Of Operations Oil And Gas Producing Activities Net Income Excluding Corporate Overhead And Interest Costs ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts	14131000	USD
CY2012	us-gaap	Results Of Operations Production Or Lifting Costs ResultsOfOperationsProductionOrLiftingCosts	23483000	USD
CY2011	us-gaap	Results Of Operations Production Or Lifting Costs ResultsOfOperationsProductionOrLiftingCosts	23820000	USD
CY2010	us-gaap	Results Of Operations Production Or Lifting Costs ResultsOfOperationsProductionOrLiftingCosts	21922000	USD
CY2011	us-gaap	Results Of Operations Revenue From Oil And Gas Producing Activities ResultsOfOperationsRevenueFromOilAndGasProducingActivities	79808000	USD
CY2010	us-gaap	Results Of Operations Revenue From Oil And Gas Producing Activities ResultsOfOperationsRevenueFromOilAndGasProducingActivities	74164000	USD
CY2012	us-gaap	Results Of Operations Revenue From Oil And Gas Producing Activities ResultsOfOperationsRevenueFromOilAndGasProducingActivities	79072000	USD
CY2011Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	476603000	USD
CY2012Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	492869000	USD
CY2012	us-gaap	Revenues From Transactions With Other Operating Segments Of Same Entity RevenuesFromTransactionsWithOtherOperatingSegmentsOfSameEntity	0	USD
CY2011	us-gaap	Revenues From Transactions With Other Operating Segments Of Same Entity RevenuesFromTransactionsWithOtherOperatingSegmentsOfSameEntity	0	USD
CY2010	us-gaap	Revenues From Transactions With Other Operating Segments Of Same Entity RevenuesFromTransactionsWithOtherOperatingSegmentsOfSameEntity	4621000	USD
CY2010	us-gaap	Revisions Of Previous Quantity Estimates RevisionsOfPreviousQuantityEstimates	27513000	USD
CY2011	us-gaap	Revisions Of Previous Quantity Estimates RevisionsOfPreviousQuantityEstimates	-58211000	USD
CY2012	us-gaap	Revisions Of Previous Quantity Estimates RevisionsOfPreviousQuantityEstimates	-86277000	USD
CY2012	us-gaap	Sales And Transfers Of Oil And Gas Produced Net Of Production Costs SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts	48905000	USD
CY2010	us-gaap	Sales And Transfers Of Oil And Gas Produced Net Of Production Costs SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts	40282000	USD
CY2011	us-gaap	Sales And Transfers Of Oil And Gas Produced Net Of Production Costs SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts	52914000	USD
CY2012	us-gaap	Sales Revenue Net SalesRevenueNet	1173884000	USD
CY2010	us-gaap	Sales Revenue Net SalesRevenueNet	1219691000	USD
CY2011	us-gaap	Sales Revenue Net SalesRevenueNet	1272188000	USD
CY2011Q3	us-gaap	Sales Revenue Net SalesRevenueNet	249523000	USD
CY2011Q4	us-gaap	Sales Revenue Net SalesRevenueNet	361181000	USD
CY2011Q2	us-gaap	Sales Revenue Net SalesRevenueNet	260649000	USD
CY2011Q1	us-gaap	Sales Revenue Net SalesRevenueNet	400835000	USD
CY2012Q2	us-gaap	Sales Revenue Net SalesRevenueNet	242363000	USD
CY2012Q1	us-gaap	Sales Revenue Net SalesRevenueNet	365851000	USD
CY2012Q3	us-gaap	Sales Revenue Net SalesRevenueNet	246808000	USD
CY2012Q4	us-gaap	Sales Revenue Net SalesRevenueNet	318862000	USD
CY2012	us-gaap	Segment Reporting Information Revenue SegmentReportingInformationRevenue	1173884000	USD
CY2011	us-gaap	Segment Reporting Information Revenue SegmentReportingInformationRevenue	1272188000	USD
CY2010	us-gaap	Segment Reporting Information Revenue SegmentReportingInformationRevenue	1215070000	USD
CY2011	us-gaap	Share Based Compensation ShareBasedCompensation	5643000	USD
CY2010	us-gaap	Share Based Compensation ShareBasedCompensation	5637000	USD
CY2012	us-gaap	Share Based Compensation ShareBasedCompensation	8271000	USD
CY2012Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	863929	shares
CY2012Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	277000000	USD
CY2011Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	345000000	USD
CY2012	us-gaap	Standardized Measure Of Discounted Future Net Cash Flow Of Proved Oil And Gas Reserves Period Increase Decrease StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease	136103000	USD
CY2011	us-gaap	Standardized Measure Of Discounted Future Net Cash Flow Of Proved Oil And Gas Reserves Period Increase Decrease StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease	203357000	USD
CY2010	us-gaap	Standardized Measure Of Discounted Future Net Cash Flow Of Proved Oil And Gas Reserves Period Increase Decrease StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease	168108000	USD
CY2009Q4	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	129108000	USD
CY2010Q4	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	168108000	USD
CY2011Q4	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	203357000	USD
CY2012Q4	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	136103000	USD
CY2011	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	3202000	USD
CY2012	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	3382000	USD
CY2010	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	3141000	USD
CY2011	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	119630000	USD
CY2010	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	4817000	USD
CY2011	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	5076000	USD
CY2012	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	6040000	USD
CY2011Q4	us-gaap	Stockholders Equity StockholdersEquity	1209336000	USD
CY2012Q4	us-gaap	Stockholders Equity StockholdersEquity	1232509000	USD
CY2010Q4	us-gaap	Stockholders Equity StockholdersEquity	1100270000	USD
CY2009Q4	us-gaap	Stockholders Equity StockholdersEquity	1084837000	USD
CY2011	us-gaap	Stockholders Equity Other StockholdersEquityOther	45000	USD
CY2010	us-gaap	Stockholders Equity Other StockholdersEquityOther	5000	USD
CY2012	us-gaap	Stockholders Equity Other StockholdersEquityOther	22000	USD
CY2011	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	33710000	USD
CY2010	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	27592000	USD
CY2012	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	40487000	USD
CY2010Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	10962	shares
CY2012Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	71782	shares
CY2011Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	32766	shares
CY2011Q4	us-gaap	Treasury Stock Value TreasuryStockValue	970000	USD
CY2012Q4	us-gaap	Treasury Stock Value TreasuryStockValue	2245000	USD
CY2010	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	-13546000	USD
CY2011	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	8693000	USD
CY2012	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	-2728000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	3533000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	8906000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	76545000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2010	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2011	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	8300000	USD
CY2011Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	6900000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	1400000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	2300000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	1400000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	0	USD
CY2012	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	151000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	0	USD
CY2011	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	2725000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	19592000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	111000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	1500000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Fifth Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary	86564000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On First Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary	187301000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Fourth Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary	97972000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Second Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary	109707000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Third Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary	108024000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Due After Five Years UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears	222002000	USD
CY2010	us-gaap	Unregulated Operating Revenue UnregulatedOperatingRevenue	109930000	USD
CY2011	us-gaap	Unregulated Operating Revenue UnregulatedOperatingRevenue	116669000	USD
CY2012	us-gaap	Unregulated Operating Revenue UnregulatedOperatingRevenue	109071000	USD
CY2012	us-gaap	Use Of Estimates UseOfEstimates	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-weight:bold;">Use of Estimates and Basis of Presentation</font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of certain assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Changes in facts and circumstances or additional information may result in revised estimates and actual results could differ materially from those estimates.</font></div></div>
CY2012	us-gaap	Utilities Operating Expense Maintenance Operations And Other Costs And Expenses UtilitiesOperatingExpenseMaintenanceOperationsAndOtherCostsAndExpenses	242367000	USD
CY2011	us-gaap	Utilities Operating Expense Maintenance Operations And Other Costs And Expenses UtilitiesOperatingExpenseMaintenanceOperationsAndOtherCostsAndExpenses	247496000	USD
CY2010	us-gaap	Utilities Operating Expense Maintenance Operations And Other Costs And Expenses UtilitiesOperatingExpenseMaintenanceOperationsAndOtherCostsAndExpenses	251375000	USD
CY2011	us-gaap	Utility Revenue UtilityRevenue	1155519000	USD
CY2010	us-gaap	Utility Revenue UtilityRevenue	1109761000	USD
CY2012	us-gaap	Utility Revenue UtilityRevenue	1064813000	USD
CY2009	us-gaap	Valuation Allowances And Reserves Adjustments ValuationAllowancesAndReservesAdjustments	0	USD
CY2010	us-gaap	Valuation Allowances And Reserves Adjustments ValuationAllowancesAndReservesAdjustments	0	USD
CY2012	us-gaap	Valuation Allowances And Reserves Adjustments ValuationAllowancesAndReservesAdjustments	0	USD
CY2009Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	2295000	USD
CY2010Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	1661000	USD
CY2008Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	3683000	USD
CY2012Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	768000	USD
CY2010	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	3042000	USD
CY2012	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	1913000	USD
CY2009	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	1898000	USD
CY2012	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	6628000	USD
CY2012	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	44073000	shares
CY2009	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	5482000	USD
CY2010	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	9045000	USD
CY2010	us-gaap	Valuation Allowances And Reserves Recoveries ValuationAllowancesAndReservesRecoveries	5369000	USD
CY2009	us-gaap	Valuation Allowances And Reserves Recoveries ValuationAllowancesAndReservesRecoveries	2196000	USD
CY2012	us-gaap	Valuation Allowances And Reserves Recoveries ValuationAllowancesAndReservesRecoveries	3822000	USD
CY2010	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39091000	shares
CY2011	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	40081000	shares
CY2012	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	43820000	shares
CY2010	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	38916000	shares
CY2011	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39864000	shares
CY2012Q4	us-gaap	Wells In Process Of Drilling WellsInProcessOfDrilling	1200
CY2010	bkh	Capitalized Interest CapitalizedInterest	4381000	USD
CY2012	bkh	Capitalized Interest CapitalizedInterest	682000	USD
CY2011	bkh	Capitalized Interest CapitalizedInterest	11260000	USD
CY2012	bkh	Capitalized Interest Of Cost Excluded From Amortization CapitalizedInterestOfCostExcludedFromAmortization	4174000	USD
CY2012Q4	bkh	Credit Exposure Non Investment Grade Company CreditExposureNonInvestmentGradeCompany	7600000	USD
CY2011Q4	bkh	Crude Oil Price Per Barrel Nymex CrudeOilPricePerBarrelNymex	96.19
CY2012Q4	bkh	Crude Oil Price Per Barrel Nymex CrudeOilPricePerBarrelNymex	94.71
CY2010Q4	bkh	Crude Oil Price Per Barrel Nymex CrudeOilPricePerBarrelNymex	79.43
CY2010Q4	bkh	Crude Oil Price Per Barrel Wellhead CrudeOilPricePerBarrelWellhead	70.82
CY2011Q4	bkh	Crude Oil Price Per Barrel Wellhead CrudeOilPricePerBarrelWellhead	88.49
CY2012Q4	bkh	Crude Oil Price Per Barrel Wellhead CrudeOilPricePerBarrelWellhead	85.31
CY2012Q4	bkh	Deferred Tax Liabilities Development Operations DeferredTaxLiabilitiesDevelopmentOperations	48411000	USD
CY2011Q4	bkh	Deferred Tax Liabilities Development Operations DeferredTaxLiabilitiesDevelopmentOperations	94334000	USD
CY2012Q4	bkh	Deferred Tax Liability State DeferredTaxLiabilityState	19986000	USD
CY2011Q4	bkh	Deferred Tax Liability State DeferredTaxLiabilityState	14611000	USD
CY2012	bkh	Defined Contribution Plan Employee Vesting Period DefinedContributionPlanEmployeeVestingPeriod	P5Y
CY2010	bkh	Effective Income Tax Rate Reconciliation Allowance For Other Funds Used During Construction Equity EffectiveIncomeTaxRateReconciliationAllowanceForOtherFundsUsedDuringConstructionEquity	-0.010
CY2012	bkh	Effective Income Tax Rate Reconciliation Allowance For Other Funds Used During Construction Equity EffectiveIncomeTaxRateReconciliationAllowanceForOtherFundsUsedDuringConstructionEquity	0.000
CY2011	bkh	Effective Income Tax Rate Reconciliation Allowance For Other Funds Used During Construction Equity EffectiveIncomeTaxRateReconciliationAllowanceForOtherFundsUsedDuringConstructionEquity	-0.005
CY2010	bkh	Effective Income Tax Rate Reconciliation Flow Through Accounting EffectiveIncomeTaxRateReconciliationFlowThroughAccounting	-0.046
CY2012	bkh	Effective Income Tax Rate Reconciliation Flow Through Accounting EffectiveIncomeTaxRateReconciliationFlowThroughAccounting	-0.013
CY2011	bkh	Effective Income Tax Rate Reconciliation Flow Through Accounting EffectiveIncomeTaxRateReconciliationFlowThroughAccounting	-0.045
CY2012	bkh	Effective Tax Rate Reconciliation Investment Tax Credits And Excess Deferred EffectiveTaxRateReconciliationInvestmentTaxCreditsAndExcessDeferred	-0.002
CY2011	bkh	Effective Tax Rate Reconciliation Investment Tax Credits And Excess Deferred EffectiveTaxRateReconciliationInvestmentTaxCreditsAndExcessDeferred	-0.005
CY2010	bkh	Effective Tax Rate Reconciliation Investment Tax Credits And Excess Deferred EffectiveTaxRateReconciliationInvestmentTaxCreditsAndExcessDeferred	-0.004
CY2012	bkh	Finite Lived Intangible Asset Purchase Accounting Adjustments FiniteLivedIntangibleAssetPurchaseAccountingAdjustments	0	USD
CY2011	bkh	Finite Lived Intangible Asset Purchase Accounting Adjustments FiniteLivedIntangibleAssetPurchaseAccountingAdjustments	0	USD
CY2010	bkh	Finite Lived Intangible Asset Purchase Accounting Adjustments FiniteLivedIntangibleAssetPurchaseAccountingAdjustments	0	USD
CY2011	bkh	Fuel Purchased Power And Cost Of Gas Sold FuelPurchasedPowerAndCostOfGasSold	574989000	USD
CY2012	bkh	Fuel Purchased Power And Cost Of Gas Sold FuelPurchasedPowerAndCostOfGasSold	407066000	USD
CY2010	bkh	Fuel Purchased Power And Cost Of Gas Sold FuelPurchasedPowerAndCostOfGasSold	566967000	USD
CY2012Q3	bkh	Gain Loss On Sale Of Oil And Gas Properties After Tax GainLossOnSaleOfOilAndGasPropertiesAfterTax	17700000	USD
CY2012Q4	bkh	Gain Loss On Sale Of Oil And Gas Properties After Tax GainLossOnSaleOfOilAndGasPropertiesAfterTax	1200000	USD
CY2012Q4	bkh	Gas And Oil Acreage Leased GasAndOilAcreageLeased	268636	acre
CY2012Q2	bkh	Impairment Of Oil And Gas Properties Net Of Tax ImpairmentOfOilAndGasPropertiesNetOfTax	17300000	USD
CY2011	bkh	Increase Decrease In Accounts Receivable And Other Current Assets IncreaseDecreaseInAccountsReceivableAndOtherCurrentAssets	4202000	USD
CY2012	bkh	Increase Decrease In Accounts Receivable And Other Current Assets IncreaseDecreaseInAccountsReceivableAndOtherCurrentAssets	2257000	USD
CY2010	bkh	Increase Decrease In Accounts Receivable And Other Current Assets IncreaseDecreaseInAccountsReceivableAndOtherCurrentAssets	18480000	USD
CY2012Q2	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	-10100000	USD
CY2011Q4	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	-900000	USD
CY2012Q4	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	3100000	USD
CY2011Q3	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	-24900000	USD
CY2011	bkh	Incremental Common Shares Attributable To Other Dilutive Securities IncrementalCommonSharesAttributableToOtherDilutiveSecurities	45000	shares
CY2012	bkh	Incremental Common Shares Attributable To Other Dilutive Securities IncrementalCommonSharesAttributableToOtherDilutiveSecurities	67000	shares
CY2011Q2	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	-5100000	USD
CY2012Q3	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	400000	USD
CY2012Q1	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	7800000	USD
CY2011Q1	bkh	Increase Decrease In Fair Value Of Unhedged Derivative Instrument Net Of Tax IncreaseDecreaseInFairValueOfUnhedgedDerivativeInstrumentNetOfTax	3600000	USD
CY2010	bkh	Incremental Common Shares Attributable To Other Dilutive Securities IncrementalCommonSharesAttributableToOtherDilutiveSecurities	25000	shares
CY2012	bkh	Incremental Common Shares Attributable To Share Based Payment Arrangements Options IncrementalCommonSharesAttributableToShareBasedPaymentArrangementsOptions	13000	shares
CY2011	bkh	Incremental Common Shares Attributable To Share Based Payment Arrangements Options IncrementalCommonSharesAttributableToShareBasedPaymentArrangementsOptions	19000	shares
CY2010	bkh	Incremental Common Shares Attributable To Share Based Payment Arrangements Options IncrementalCommonSharesAttributableToShareBasedPaymentArrangementsOptions	14000	shares
CY2010	bkh	Incremental Common Shares Attributable To Share Based Payment Arrangements Restricted Stock And Restricted Stock Units IncrementalCommonSharesAttributableToShareBasedPaymentArrangementsRestrictedStockAndRestrictedStockUnits	107000	shares
CY2012	bkh	Incremental Common Shares Attributable To Share Based Payment Arrangements Restricted Stock And Restricted Stock Units IncrementalCommonSharesAttributableToShareBasedPaymentArrangementsRestrictedStockAndRestrictedStockUnits	173000	shares
CY2011	bkh	Incremental Common Shares Attributable To Share Based Payment Arrangements Restricted Stock And Restricted Stock Units IncrementalCommonSharesAttributableToShareBasedPaymentArrangementsRestrictedStockAndRestrictedStockUnits	153000	shares
CY2012	bkh	Incremental Shares Attributable To Equity Forward Agreement IncrementalSharesAttributableToEquityForwardAgreement	0	shares
CY2011	bkh	Incremental Shares Attributable To Equity Forward Agreement IncrementalSharesAttributableToEquityForwardAgreement	0	shares
CY2010	bkh	Incremental Shares Attributable To Equity Forward Agreement IncrementalSharesAttributableToEquityForwardAgreement	29000	shares
CY2011Q2	bkh	Market Price Per Share Low MarketPricePerShareLow	28.12
CY2011Q3	bkh	Market Price Per Share Low MarketPricePerShareLow	25.83
CY2011Q4	bkh	Market Price Per Share Low MarketPricePerShareLow	29.10
CY2011Q1	bkh	Market Price Per Share Low MarketPricePerShareLow	29.76
CY2012Q2	bkh	Market Price Per Share Low MarketPricePerShareLow	31.32
CY2012Q1	bkh	Market Price Per Share Low MarketPricePerShareLow	32.18
CY2012Q3	bkh	Market Price Per Share Low MarketPricePerShareLow	30.29
CY2012Q4	bkh	Market Price Per Share Low MarketPricePerShareLow	33.51
CY2011Q1	bkh	Market Prices Per Share High MarketPricesPerShareHigh	33.64
CY2011Q4	bkh	Market Prices Per Share High MarketPricesPerShareHigh	34.47
CY2011Q3	bkh	Market Prices Per Share High MarketPricesPerShareHigh	32.22
CY2011Q2	bkh	Market Prices Per Share High MarketPricesPerShareHigh	34.85
CY2012Q3	bkh	Market Prices Per Share High MarketPricesPerShareHigh	36.28
CY2012Q1	bkh	Market Prices Per Share High MarketPricesPerShareHigh	35.82
CY2012Q2	bkh	Market Prices Per Share High MarketPricesPerShareHigh	34.31
CY2012Q4	bkh	Market Prices Per Share High MarketPricesPerShareHigh	37.00
CY2012Q4	bkh	Natural Gas Price Per Mcf Nymex NaturalGasPricePerMcfNymex	2.76
CY2011Q4	bkh	Natural Gas Price Per Mcf Nymex NaturalGasPricePerMcfNymex	4.12
CY2010Q4	bkh	Natural Gas Price Per Mcf Nymex NaturalGasPricePerMcfNymex	4.38
CY2010Q4	bkh	Natural Gas Price Per Mcf Wellhead NaturalGasPricePerMcfWellhead	3.45
CY2011Q4	bkh	Natural Gas Price Per Mcf Wellhead NaturalGasPricePerMcfWellhead	3.59
CY2012Q4	bkh	Natural Gas Price Per Mcf Wellhead NaturalGasPricePerMcfWellhead	2.24
CY2010	bkh	Non Cash Revision To Capitalized Asset Retirement Costs NonCashRevisionToCapitalizedAssetRetirementCosts	-1858000	USD
CY2012	bkh	Non Cash Revision To Capitalized Asset Retirement Costs NonCashRevisionToCapitalizedAssetRetirementCosts	5743000	USD
CY2011	bkh	Non Cash Revision To Capitalized Asset Retirement Costs NonCashRevisionToCapitalizedAssetRetirementCosts	-1525000	USD
CY2012	bkh	Number Of Business Groups NumberOfBusinessGroups	2	Business_Group
CY2012	bkh	Proved Undeveloped Reserves Extensions Discoveries And Additions ProvedUndevelopedReservesExtensionsDiscoveriesAndAdditions	5600000	Mcfe
CY2012	bkh	Public Utilities Allowance For Funds Used During Construction Interest Costs Capitalized PublicUtilitiesAllowanceForFundsUsedDuringConstructionInterestCostsCapitalized	3462000	USD
CY2010	bkh	Public Utilities Allowance For Funds Used During Construction Interest Costs Capitalized PublicUtilitiesAllowanceForFundsUsedDuringConstructionInterestCostsCapitalized	10689000	USD
CY2011	bkh	Public Utilities Allowance For Funds Used During Construction Interest Costs Capitalized PublicUtilitiesAllowanceForFundsUsedDuringConstructionInterestCostsCapitalized	14041000	USD
CY2012Q4	bkh	Pud Locations In Reserves For Five Or More Years PudLocationsInReservesForFiveOrMoreYears	0	PUD_Location
CY2012	bkh	Reserves Replaced ReservesReplaced	0.46
CY2012	bkh	Results Of Operations Gain Loss On Sale ResultsOfOperationsGainLossOnSale	29129000	USD
CY2011	bkh	Results Of Operations Gain Loss On Sale ResultsOfOperationsGainLossOnSale	0	USD
CY2010	bkh	Results Of Operations Gain Loss On Sale ResultsOfOperationsGainLossOnSale	0	USD
CY2011	bkh	Total Other Income Expense TotalOtherIncomeExpense	-128771000	USD
CY2010	bkh	Total Other Income Expense TotalOtherIncomeExpense	-99669000	USD
CY2012	bkh	Total Other Income Expense TotalOtherIncomeExpense	-106816000	USD
CY2011	bkh	Unregulated Energy Operating Costs UnregulatedEnergyOperatingCosts	93453000	USD
CY2012	bkh	Unregulated Energy Operating Costs UnregulatedEnergyOperatingCosts	85830000	USD
CY2010	bkh	Unregulated Energy Operating Costs UnregulatedEnergyOperatingCosts	71672000	USD
CY2012	dei	Amendment Flag AmendmentFlag	false
CY2012	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2012	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2012	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2012
CY2012	dei	Document Period End Date DocumentPeriodEndDate	2012-12-31
CY2012	dei	Document Type DocumentType	10-K
CY2012	dei	Entity Central Index Key EntityCentralIndexKey	0001130464
CY2013Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	44222903	shares
CY2012	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2012	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2012Q2	dei	Entity Public Float EntityPublicFloat	1400316896	USD
CY2012	dei	Entity Registrant Name EntityRegistrantName	BLACK HILLS CORP /SD/
CY2012	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2012	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes

Files In Submission

Name	View Source	Status
0001130464-13-000071-index-headers.html	Edgar Link	pending
0001130464-13-000071-index.html	Edgar Link	pending
0001130464-13-000071.txt	Edgar Link	pending
0001130464-13-000071-xbrl.zip	Edgar Link	pending
bkh-20121231.xml	Edgar Link	completed
bkh-20121231.xsd	Edgar Link	pending
bkh-20121231_cal.xml	Edgar Link	unprocessable
bkh-20121231_def.xml	Edgar Link	unprocessable
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bkh-20121231_pre.xml	Edgar Link	unprocessable
bkh10k12312012.htm	Edgar Link	pending
bkhex-1015122012.htm	Edgar Link	pending
bkhex-21123112.htm	Edgar Link	pending
bkhex-231122012.htm	Edgar Link	pending
bkhex-232123112.htm	Edgar Link	pending
bkhex-311122012.htm	Edgar Link	pending
bkhex-312122012.htm	Edgar Link	pending
bkhex-321122012.htm	Edgar Link	pending
bkhex-322122012.htm	Edgar Link	pending
exhibit95minesafetydata122.htm	Edgar Link	pending
exhibit99oilandgas122012.htm	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xls	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
R100.htm	Edgar Link	pending
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$BKH
BLACK HILLS CORP /SD/ Stock $bkh

2012 Q4 Form 10-K Financial Statement

#000113046413000071 Filed on February 25, 2013

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$BKH BLACK HILLS CORP /SD/ Stock $bkh

2012 Q4 Form 10-K Financial Statement

#000113046413000071 Filed on February 25, 2013

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$BKH
BLACK HILLS CORP /SD/ Stock $bkh