$NFG
NATIONAL FUEL GAS CO Stock $nfg

$nfg Overview Financials Valuation SEC Filings Company Website

2017 Q3 Form 10-K Financial Statement

#000007014517000054 Filed on November 17, 2017

Income Statement

Concept	2017 Q3	2016 Q3	2016 Q2
Revenue	$286.9M	$292.5M	$335.6M
YoY Change	-1.9%	-2.86%	-1.24%
Cost Of Revenue	$10.90M	$800.0K	$23.50M
YoY Change	1262.5%	-84.91%	-12.96%
Gross Profit	$276.0M	$291.7M	$312.1M
YoY Change	-5.38%	-1.39%	-0.22%
Gross Profit Margin	96.19%	99.73%	93.0%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$55.40M	$56.10M	$58.80M
YoY Change	-1.25%	-20.87%	-26.37%
% of Gross Profit	20.07%	19.23%	18.84%
Operating Expenses	$147.7M	$177.6M	$290.5M
YoY Change	-16.84%	-13.49%	-64.96%
Operating Profit	$87.40M	$81.24M	$45.16M
YoY Change	7.57%	-124.87%	-109.23%
Interest Expense	-$32.80M	-$27.50M	-$29.70M
YoY Change	19.27%	2.23%	29.69%
% of Operating Profit	-37.53%	-33.85%	-65.76%
Other Income/Expense, Net	-$34.50M	$2.900M	$1.500M
YoY Change	-1289.66%	-14.71%	-28.57%
Pretax Income	$61.10M	$56.60M	$17.03M
YoY Change	7.95%	-116.16%	-103.34%
Income Tax	$15.50M	$19.10M	$8.740M
% Of Pretax Income	25.37%	33.75%	51.33%
Net Earnings	$45.58M	$37.55M	$8.286M
YoY Change	21.37%	-120.01%	-102.83%
Net Earnings / Revenue	15.88%	12.84%	2.47%
Basic Earnings Per Share	$0.53	$0.44	$0.10
Diluted Earnings Per Share	$0.53	$0.44	$0.10
COMMON SHARES
Basic Shares Outstanding	85.51M shares	84.99M shares	84.92M shares
Diluted Shares Outstanding			85.47M shares

Balance Sheet

Concept	2017 Q3	2016 Q3	2016 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$555.5M	$130.0M	$105.6M
YoY Change	327.31%	14.44%	-65.94%
Cash & Equivalents	$555.5M	$130.0M	$105.6M
Short-Term Investments
Other Short-Term Assets	$51.51M	$59.35M	$47.12M
YoY Change	-13.22%	-2.16%	-4.71%
Inventory	$69.60M	$68.20M	$49.00M
Prepaid Expenses
Receivables	$112.4M	$133.2M	$140.9M
Other Receivables	$9.700M	$15.70M	$8.100M
Total Short-Term Assets	$818.3M	$413.0M	$361.1M
YoY Change	98.12%	9.91%	-40.94%
LONG-TERM ASSETS
Property, Plant & Equipment	$4.674B	$4.454B	$4.448B
YoY Change	4.93%	-16.46%	-18.86%
Goodwill	$5.476M	$5.476M	$5.476M
YoY Change	0.0%	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments	$125.3M	$110.7M	$111.4M
YoY Change	13.19%	19.03%	25.17%
Other Assets	$742.0K	$604.0K	$116.0K
YoY Change	22.85%	261.68%	-32.56%
Total Long-Term Assets	$611.0M	$768.9M	$732.3M
YoY Change	-20.54%	-10.31%	-8.05%
TOTAL ASSETS
Total Short-Term Assets	$818.3M	$413.0M	$361.1M
Total Long-Term Assets	$611.0M	$768.9M	$732.3M
Total Assets	$6.103B	$5.636B	$5.541B
YoY Change	8.28%	-14.14%	-19.57%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$126.4M	$108.1M	$86.49M
YoY Change	17.02%	-40.1%	-37.28%
Accrued Expenses	$111.9M	$32.91M	$24.84M
YoY Change	240.0%	7.18%	-9.64%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due	$300.0M	$0.00	$0.00
YoY Change
Total Short-Term Liabilities	$646.0M	$303.7M	$276.3M
YoY Change	112.7%	-31.92%	-34.19%
LONG-TERM LIABILITIES
Long-Term Debt	$2.084B	$2.086B	$2.086B
YoY Change	-0.12%	0.11%	-0.63%
Other Long-Term Liabilities	$778.6M	$895.6M	$843.6M
YoY Change	-13.06%	2.78%	6.15%
Total Long-Term Liabilities	$1.670B	$1.719B	$1.652B
YoY Change	-2.88%	-14.43%	-22.22%
TOTAL LIABILITIES
Total Short-Term Liabilities	$646.0M	$303.7M	$276.3M
Total Long-Term Liabilities	$1.670B	$1.719B	$1.652B
Total Liabilities	$2.316B	$2.023B	$1.928B
YoY Change	14.47%	-17.61%	-24.2%
SHAREHOLDERS EQUITY
Retained Earnings	$851.7M	$676.4M	$673.3M
YoY Change	25.92%	-38.69%	-49.16%
Common Stock	$85.54M	$85.12M	$84.95M
YoY Change	0.5%	0.62%	0.5%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$1.704B	$1.527B	$1.528B
YoY Change
Total Liabilities & Shareholders Equity	$6.103B	$5.636B	$5.541B
YoY Change	8.28%	-14.14%	-19.57%

Cashflow Statement

Concept	2017 Q3	2016 Q3	2016 Q2
OPERATING ACTIVITIES
Net Income	$45.58M	$37.55M	$8.286M
YoY Change	21.37%	-120.01%	-102.83%
Depreciation, Depletion And Amortization	$55.40M	$56.10M	$58.80M
YoY Change	-1.25%	-20.87%	-26.37%
Cash From Operating Activities	$133.4M	$129.0M	$147.2M
YoY Change	3.41%	-8.51%	-28.23%
INVESTING ACTIVITIES
Capital Expenditures	-$135.5M	-$99.80M	-$122.8M
YoY Change	35.77%	-66.64%	-45.59%
Acquisitions
YoY Change
Other Investing Activities	$11.40M	$24.00M	$17.40M
YoY Change	-52.5%	-536.36%	8600.0%
Cash From Investing Activities	-$124.2M	-$75.80M	-$105.4M
YoY Change	63.85%	-75.13%	-53.24%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	261.3M	-28.80M	-29.90M
YoY Change	-1007.29%	-11.66%	-111.46%
NET CHANGE
Cash From Operating Activities	133.4M	129.0M	147.2M
Cash From Investing Activities	-124.2M	-75.80M	-105.4M
Cash From Financing Activities	261.3M	-28.80M	-29.90M
Net Change In Cash	270.5M	24.40M	11.90M
YoY Change	1008.61%	-112.42%	-95.05%
FREE CASH FLOW
Cash From Operating Activities	$133.4M	$129.0M	$147.2M
Capital Expenditures	-$135.5M	-$99.80M	-$122.8M
Free Cash Flow	$268.9M	$228.8M	$270.0M
YoY Change	17.53%	-48.02%	-37.33%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2017	dei	Amendment Flag AmendmentFlag	false
CY2017	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--09-30
CY2017	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2017	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2017
CY2017	dei	Document Period End Date DocumentPeriodEndDate	2017-09-30
CY2017	dei	Document Type DocumentType	10-K
CY2017	dei	Entity Central Index Key EntityCentralIndexKey	0000070145
CY2017Q4	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	85582201	shares
CY2017	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2017	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2017Q1	dei	Entity Public Float EntityPublicFloat	4970818000	USD
CY2017	dei	Entity Registrant Name EntityRegistrantName	NATIONAL FUEL GAS CO
CY2017	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2017	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2017	nfg	After Tax Net Hedging Gains Losses In Accumulated Other Comprehensive Income Loss AfterTaxNetHedgingGainsLossesInAccumulatedOtherComprehensiveIncomeLoss	20800000	USD
CY2017	nfg	Amortization Period AmortizationPeriod	P10Y
CY2015	nfg	Amount Spent For Developing Proved Undeveloped Reserves AmountSpentForDevelopingProvedUndevelopedReserves	161800000	USD
CY2016	nfg	Amount Spent For Developing Proved Undeveloped Reserves AmountSpentForDevelopingProvedUndevelopedReserves	92800000	USD
CY2017	nfg	Amount Spent For Developing Proved Undeveloped Reserves AmountSpentForDevelopingProvedUndevelopedReserves	101100000	USD
CY2017	nfg	Amount Which Could Trigger Repayment Obligation Under Committed Credit Facility AmountWhichCouldTriggerRepaymentObligationUnderCommittedCreditFacility	40000000	USD
CY2017	nfg	Annual Discount For Estimated Timing Of Cash Flows AnnualDiscountForEstimatedTimingOfCashFlows	0.10
CY2017	nfg	Appalachian Region Wells Developed AppalachianRegionWellsDeveloped	37
CY2015	nfg	Beginning Retained Earnings Unappropriated And Current Period Net Income Loss BeginningRetainedEarningsUnappropriatedAndCurrentPeriodNetIncomeLoss	1234934000	USD
CY2016	nfg	Beginning Retained Earnings Unappropriated And Current Period Net Income Loss BeginningRetainedEarningsUnappropriatedAndCurrentPeriodNetIncomeLoss	812242000	USD
CY2017	nfg	Beginning Retained Earnings Unappropriated And Current Period Net Income Loss BeginningRetainedEarningsUnappropriatedAndCurrentPeriodNetIncomeLoss	959843000	USD
CY2016	nfg	Capital Expenditures Related To Proved Undeveloped Reserves CapitalExpendituresRelatedToProvedUndevelopedReserves	93000000	USD
CY2017	nfg	Capital Expenditures Related To Proved Undeveloped Reserves CapitalExpendituresRelatedToProvedUndevelopedReserves	101000000	USD
CY2017	nfg	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months After Tax CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonthsAfterTax	10600000	USD
CY2016	nfg	Conversion Of Undeveloped Proved Reserves To Developed Proved Reserves Volume ConversionOfUndevelopedProvedReservesToDevelopedProvedReservesVolume	92000000000	ft3
CY2017	nfg	Conversion Of Undeveloped Proved Reserves To Developed Proved Reserves Volume ConversionOfUndevelopedProvedReservesToDevelopedProvedReservesVolume	147000000000	ft3
CY2016Q3	nfg	Cost Of Removal Regulatory Liability CostOfRemovalRegulatoryLiability	193424000	USD
CY2017Q3	nfg	Cost Of Removal Regulatory Liability CostOfRemovalRegulatoryLiability	204630000	USD
CY2015	nfg	Costs Incurred Development Costs Capitalized Interest CostsIncurredDevelopmentCostsCapitalizedInterest	500000	USD
CY2016	nfg	Costs Incurred Development Costs Capitalized Interest CostsIncurredDevelopmentCostsCapitalizedInterest	200000	USD
CY2017	nfg	Costs Incurred Development Costs Capitalized Interest CostsIncurredDevelopmentCostsCapitalizedInterest	200000	USD
CY2015	nfg	Costs Incurred Exploration Costs Capitalized Interest CostsIncurredExplorationCostsCapitalizedInterest	400000	USD
CY2016	nfg	Costs Incurred Exploration Costs Capitalized Interest CostsIncurredExplorationCostsCapitalizedInterest	300000	USD
CY2017	nfg	Costs Incurred Exploration Costs Capitalized Interest CostsIncurredExplorationCostsCapitalizedInterest	300000	USD
CY2017	nfg	Debt Instrument Principal Outstanding Portion Of Long Term Debt DebtInstrumentPrincipalOutstandingPortionOfLongTermDebt	0.041
CY2017	nfg	Debt To Capitalization Ratio DebtToCapitalizationRatio	0.58
CY2016Q3	nfg	Deferred Tax Assets Pension And Other Post Retirement Costs DeferredTaxAssetsPensionAndOtherPostRetirementCosts	195829000	USD
CY2017Q3	nfg	Deferred Tax Assets Pension And Other Post Retirement Costs DeferredTaxAssetsPensionAndOtherPostRetirementCosts	123532000	USD
CY2016Q3	nfg	Deferred Tax Liabilities Pension And Other Post Retirement Costs DeferredTaxLiabilitiesPensionAndOtherPostRetirementCosts	151903000	USD
CY2017Q3	nfg	Deferred Tax Liabilities Pension And Other Post Retirement Costs DeferredTaxLiabilitiesPensionAndOtherPostRetirementCosts	79516000	USD
CY2016Q3	nfg	Depreciable Plant Assets DepreciablePlantAssets	9167865000	USD
CY2017Q3	nfg	Depreciable Plant Assets DepreciablePlantAssets	9570679000	USD
CY2015	nfg	Depreciation Depletion And Amortization Per Mcfe Of Production DepreciationDepletionAndAmortizationPerMcfeOfProduction	1.49	USD
CY2016	nfg	Depreciation Depletion And Amortization Per Mcfe Of Production DepreciationDepletionAndAmortizationPerMcfeOfProduction	0.85	USD
CY2017	nfg	Depreciation Depletion And Amortization Per Mcfe Of Production DepreciationDepletionAndAmortizationPerMcfeOfProduction	0.63	USD
CY2017Q3	nfg	Earnings Reinvested In Business Available For Dividends EarningsReinvestedInBusinessAvailableForDividends	707500000	USD
CY2015	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Cost Of Covered Prescription Drug Benefits EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaCostOfCoveredPrescriptionDrugBenefits	0.0717
CY2016	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Cost Of Covered Prescription Drug Benefits EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaCostOfCoveredPrescriptionDrugBenefits	0.0900
CY2017	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Cost Of Covered Prescription Drug Benefits EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaCostOfCoveredPrescriptionDrugBenefits	0.0845
CY2015	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Medicare Part B Reimbursement EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaMedicarePartBReimbursement	0.0668
CY2016	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Medicare Part B Reimbursement EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaMedicarePartBReimbursement	0.0475
CY2017	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Medicare Part B Reimbursement EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaMedicarePartBReimbursement	0.0475
CY2015	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Medicare Part D Subsidy EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaMedicarePartDSubsidy	0.0665
CY2016	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Medicare Part D Subsidy EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaMedicarePartDSubsidy	0.0720
CY2017	nfg	Estimated Gross Other Post Retirement Benefit Payments Annual Rate Of Increase In Per Capita Medicare Part D Subsidy EstimatedGrossOtherPostRetirementBenefitPaymentsAnnualRateOfIncreaseInPerCapitaMedicarePartDSubsidy	0.0733
CY2015	nfg	Estimated Gross Other Post Retirement Benefit Payments Rate Of Increase For Post Age Sixty Five Participants EstimatedGrossOtherPostRetirementBenefitPaymentsRateOfIncreaseForPostAgeSixtyFiveParticipants	0.0668
CY2016	nfg	Estimated Gross Other Post Retirement Benefit Payments Rate Of Increase For Post Age Sixty Five Participants EstimatedGrossOtherPostRetirementBenefitPaymentsRateOfIncreaseForPostAgeSixtyFiveParticipants	0.0475
CY2017	nfg	Estimated Gross Other Post Retirement Benefit Payments Rate Of Increase For Post Age Sixty Five Participants EstimatedGrossOtherPostRetirementBenefitPaymentsRateOfIncreaseForPostAgeSixtyFiveParticipants	0.0475
CY2015	nfg	Estimated Gross Other Post Retirement Benefit Payments Rate Of Increase For Pre Age Sixty Five Participants EstimatedGrossOtherPostRetirementBenefitPaymentsRateOfIncreaseForPreAgeSixtyFiveParticipants	0.0693
CY2016	nfg	Estimated Gross Other Post Retirement Benefit Payments Rate Of Increase For Pre Age Sixty Five Participants EstimatedGrossOtherPostRetirementBenefitPaymentsRateOfIncreaseForPreAgeSixtyFiveParticipants	0.0575
CY2017	nfg	Estimated Gross Other Post Retirement Benefit Payments Rate Of Increase For Pre Age Sixty Five Participants EstimatedGrossOtherPostRetirementBenefitPaymentsRateOfIncreaseForPreAgeSixtyFiveParticipants	0.0567
CY2016Q3	nfg	Fair Value Assets Liabilities Measured On Recurring Basis Net FairValueAssetsLiabilitiesMeasuredOnRecurringBasisNet	298188000	USD
CY2017Q3	nfg	Fair Value Assets Liabilities Measured On Recurring Basis Net FairValueAssetsLiabilitiesMeasuredOnRecurringBasisNet	650637000	USD
CY2016Q3	nfg	Fair Value Assets Measured On Recurring Basis Total FairValueAssetsMeasuredOnRecurringBasisTotal	299650000	USD
CY2017Q3	nfg	Fair Value Assets Measured On Recurring Basis Total FairValueAssetsMeasuredOnRecurringBasisTotal	651740000	USD
CY2016Q3	nfg	Fair Value Liabilities Measured On Recurring Basis Total FairValueLiabilitiesMeasuredOnRecurringBasisTotal	1462000	USD
CY2017Q3	nfg	Fair Value Liabilities Measured On Recurring Basis Total FairValueLiabilitiesMeasuredOnRecurringBasisTotal	1103000	USD
CY2017Q3	nfg	Full Cost Ceiling Exceeds Book Value Of Oil And Gas Properties FullCostCeilingExceedsBookValueOfOilAndGasProperties	286400000	USD
CY2017Q3	nfg	Full Cost Ceiling Test Discount Factor FullCostCeilingTestDiscountFactor	0.10
CY2015	nfg	Impairmentof Oiland Gas Producing Properties ImpairmentofOilandGasProducingProperties	1126257000	USD
CY2016Q3	nfg	Other Current Assets Fair Values Of Firm Commitments OtherCurrentAssetsFairValuesOfFirmCommitments	3962000	USD
CY2017Q3	nfg	Other Current Assets Fair Values Of Firm Commitments OtherCurrentAssetsFairValuesOfFirmCommitments	1031000	USD
CY2015Q4	nfg	Impairmentof Oiland Gas Producing Properties ImpairmentofOilandGasProducingProperties	435500000	USD
CY2016Q1	nfg	Impairmentof Oiland Gas Producing Properties ImpairmentofOilandGasProducingProperties	397400000	USD
CY2016Q2	nfg	Impairmentof Oiland Gas Producing Properties ImpairmentofOilandGasProducingProperties	82700000	USD
CY2016Q3	nfg	Impairmentof Oiland Gas Producing Properties ImpairmentofOilandGasProducingProperties	32700000	USD
CY2016	nfg	Impairmentof Oiland Gas Producing Properties ImpairmentofOilandGasProducingProperties	948307000	USD
CY2017	nfg	Impairmentof Oiland Gas Producing Properties ImpairmentofOilandGasProducingProperties	0	USD
CY2015Q4	nfg	Impairmentof Oiland Gas Producing Properties After Tax ImpairmentofOilandGasProducingPropertiesAfterTax	252600000	USD
CY2016Q1	nfg	Impairmentof Oiland Gas Producing Properties After Tax ImpairmentofOilandGasProducingPropertiesAfterTax	230500000	USD
CY2016Q2	nfg	Impairmentof Oiland Gas Producing Properties After Tax ImpairmentofOilandGasProducingPropertiesAfterTax	47900000	USD
CY2016Q3	nfg	Impairmentof Oiland Gas Producing Properties After Tax ImpairmentofOilandGasProducingPropertiesAfterTax	19000000	USD
CY2015	nfg	Income From Continuing Operations Before Income Taxes IncomeFromContinuingOperationsBeforeIncomeTaxes	-698977000	USD
CY2016	nfg	Income From Continuing Operations Before Income Taxes IncomeFromContinuingOperationsBeforeIncomeTaxes	-523855000	USD
CY2017	nfg	Income From Continuing Operations Before Income Taxes IncomeFromContinuingOperationsBeforeIncomeTaxes	443991000	USD
CY2015	nfg	Income Tax Expense Benefit Including Deferred Investment Tax Credit IncomeTaxExpenseBenefitIncludingDeferredInvestmentTaxCredit	-319550000	USD
CY2016	nfg	Income Tax Expense Benefit Including Deferred Investment Tax Credit IncomeTaxExpenseBenefitIncludingDeferredInvestmentTaxCredit	-232897000	USD
CY2017	nfg	Income Tax Expense Benefit Including Deferred Investment Tax Credit IncomeTaxExpenseBenefitIncludingDeferredInvestmentTaxCredit	160509000	USD
CY2016Q3	nfg	Interest Payable On Long Term Debt InterestPayableOnLongTermDebt	34900000	USD
CY2017Q3	nfg	Interest Payable On Long Term Debt InterestPayableOnLongTermDebt	35031000	USD
CY2017	nfg	Lineof Credit Facility Term Start Date LineofCreditFacilityTermStartDate	2017-10-01
CY2017Q3	nfg	Maximum Debt Increase Under Existing Indenture Covenants MaximumDebtIncreaseUnderExistingIndentureCovenants	126000000	USD
CY2017	nfg	Number Of Registered Shareholders Of Common Stock NumberOfRegisteredShareholdersOfCommonStock	11211
CY2017	nfg	Offsetting Gain Loss On Hedged Item Attributable To Hedged Risk OffsettingGainLossOnHedgedItemAttributableToHedgedRisk	-2119000	USD
CY2017Q3	nfg	Operating Loss Carryforwards Annual Limitations OperatingLossCarryforwardsAnnualLimitations	1800000	USD
CY2016Q3	nfg	Other Investments Including Csv Life Insurance And Avail For Sale OtherInvestmentsIncludingCsvLifeInsuranceAndAvailForSale	110664000	USD
CY2017Q3	nfg	Other Investments Including Csv Life Insurance And Avail For Sale OtherInvestmentsIncludingCsvLifeInsuranceAndAvailForSale	125265000	USD
CY2017	nfg	Percent Wells Developed PercentWellsDeveloped	0.41
CY2017Q3	nfg	Percentage Of Assets Or Earning Power That Are Sold Or Transferred PercentageOfAssetsOrEarningPowerThatAreSoldOrTransferred	0.50
CY2017	nfg	Percentage Of Voting Power To Redeem Rights PercentageOfVotingPowerToRedeemRights	0.75
CY2017	nfg	Percentageof Voting Power PercentageofVotingPower	0.10
CY2017Q3	nfg	Project Costs ProjectCosts	75800000	USD
CY2016Q3	nfg	Proved Undeveloped Reserves Additions ProvedUndevelopedReservesAdditions	102000000000	ft3
CY2017Q3	nfg	Proved Undeveloped Reserves Additions ProvedUndevelopedReservesAdditions	269000000000	ft3
CY2015	nfg	Proved Undeveloped Reserves As Percentage Of Total Proved Reserves ProvedUndevelopedReservesAsPercentageOfTotalProvedReserves	0.35
CY2016	nfg	Proved Undeveloped Reserves As Percentage Of Total Proved Reserves ProvedUndevelopedReservesAsPercentageOfTotalProvedReserves	0.29
CY2017	nfg	Proved Undeveloped Reserves As Percentage Of Total Proved Reserves ProvedUndevelopedReservesAsPercentageOfTotalProvedReserves	0.28
CY2016Q3	nfg	Proved Undeveloped Reserves Conversions To Developed Reserves ProvedUndevelopedReservesConversionsToDevelopedReserves	110000000000	ft3
CY2017Q3	nfg	Proved Undeveloped Reserves Conversions To Developed Reserves ProvedUndevelopedReservesConversionsToDevelopedReserves	159000000000	ft3
CY2016Q3	nfg	Proved Undeveloped Reserves Decrease ProvedUndevelopedReservesDecrease	284000000000	ft3
CY2016Q3	nfg	Proved Undeveloped Reserves Downward Revisions ProvedUndevelopedReservesDownwardRevisions	14000000000	ft3
CY2017Q3	nfg	Proved Undeveloped Reserves Increase ProvedUndevelopedReservesIncrease	69000000000	ft3
CY2013Q3	nfg	Proved Undeveloped Reserves Percentage ProvedUndevelopedReservesPercentage	0.39
CY2014Q3	nfg	Proved Undeveloped Reserves Percentage ProvedUndevelopedReservesPercentage	0.51
CY2015Q3	nfg	Proved Undeveloped Reserves Percentage ProvedUndevelopedReservesPercentage	0.33
CY2016Q3	nfg	Proved Undeveloped Reserves Percentage ProvedUndevelopedReservesPercentage	0.11
CY2017Q3	nfg	Proved Undeveloped Reserves Percentage ProvedUndevelopedReservesPercentage	0.27
CY2016Q3	nfg	Proved Undeveloped Reserves Removed ProvedUndevelopedReservesRemoved	96000000000	ft3
CY2017Q3	nfg	Proved Undeveloped Reserves Removed ProvedUndevelopedReservesRemoved	54000000000	ft3
CY2016Q3	nfg	Proved Undeveloped Reserves Sales ProvedUndevelopedReservesSales	166000000000	ft3
CY2017Q3	nfg	Proved Undeveloped Reserves Upward Revisions ProvedUndevelopedReservesUpwardRevisions	-13000000000	ft3
CY2017	nfg	Recommended Costof Equity RecommendedCostofEquity	0.086
CY2017	nfg	Recommended Equity Ratio RecommendedEquityRatio	0.423
CY2017	nfg	Recommendedrateincreasedecreaseamount Recommendedrateincreasedecreaseamount	8500000	USD
CY2016Q3	nfg	Recoverable Future Taxes RecoverableFutureTaxes	177261000	USD
CY2017Q3	nfg	Recoverable Future Taxes RecoverableFutureTaxes	181363000	USD
CY2017	nfg	Redemption Price For Shareholder Rights Under Shareholder Rights Plan RedemptionPriceForShareholderRightsUnderShareholderRightsPlan	0.005
CY2016	nfg	Reimbursed Drilling Carry Costsfor Jda Partner ReimbursedDrillingCarryCostsforJDAPartner	36000000	USD
CY2015	nfg	Results Of Operations Franchise Or Ad Valorem Taxes ResultsOfOperationsFranchiseOrAdValoremTaxes	20167000	USD
CY2016	nfg	Results Of Operations Franchise Or Ad Valorem Taxes ResultsOfOperationsFranchiseOrAdValoremTaxes	13794000	USD
CY2017	nfg	Results Of Operations Franchise Or Ad Valorem Taxes ResultsOfOperationsFranchiseOrAdValoremTaxes	15372000	USD
CY2015	nfg	Results Of Operations Sales Revenue To Affiliated Enterprises ResultsOfOperationsSalesRevenueToAffiliatedEnterprises	0	USD
CY2016	nfg	Results Of Operations Sales Revenue To Affiliated Enterprises ResultsOfOperationsSalesRevenueToAffiliatedEnterprises	0	USD
CY2017	nfg	Results Of Operations Sales Revenue To Affiliated Enterprises ResultsOfOperationsSalesRevenueToAffiliatedEnterprises	0	USD
CY2015	nfg	Resultsof Operations Purchased Emission Allowance Expense ResultsofOperationsPurchasedEmissionAllowanceExpense	3089000	USD
CY2016	nfg	Resultsof Operations Purchased Emission Allowance Expense ResultsofOperationsPurchasedEmissionAllowanceExpense	700000	USD
CY2017	nfg	Resultsof Operations Purchased Emission Allowance Expense ResultsofOperationsPurchasedEmissionAllowanceExpense	1391000	USD
CY2017	nfg	Shareholder Rights Plan Expiration Date ShareholderRightsPlanExpirationDate	2018-07-31
CY2016Q3	nfg	Taxes Refundable To Customers TaxesRefundableToCustomers	93318000	USD
CY2017Q3	nfg	Taxes Refundable To Customers TaxesRefundableToCustomers	95739000	USD
CY2016Q3	nfg	Unamortized Debt Expense UnamortizedDebtExpense	1688000	USD
CY2017Q3	nfg	Unamortized Debt Expense UnamortizedDebtExpense	1159000	USD
CY2016Q3	us-gaap	Accounts Payable Current AccountsPayableCurrent	108056000	USD
CY2017Q3	us-gaap	Accounts Payable Current AccountsPayableCurrent	126443000	USD
CY2016Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	18382000	USD
CY2017Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	22883000	USD
CY2016Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	5085099000	USD
CY2017Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	5271486000	USD
CY2015Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	93372000	USD
CY2016Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-5640000	USD
CY2017Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-30123000	USD
CY2015	us-gaap	Acquisition Costs AcquisitionCosts	0	USD
CY2016	us-gaap	Acquisition Costs AcquisitionCosts	0	USD
CY2017	us-gaap	Acquisition Costs AcquisitionCosts	0	USD
CY2016Q3	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	771164000	USD
CY2017Q3	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	796646000	USD
CY2015	us-gaap	Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation	9064000	USD
CY2016	us-gaap	Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation	1868000	USD
CY2015	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	2100000	USD
CY2016	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	4800000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	10800000	USD
CY2016Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	21109000	USD
CY2017Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	22526000	USD
CY2015	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	709063	shares
CY2016	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	431408	shares
CY2017	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	157649	shares
CY2014Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	117713000	USD
CY2015Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	156805000	USD
CY2016Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	112330000	USD
CY2017Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	106395000	USD
CY2015	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	7767000	USD
CY2016	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	8300000	USD
CY2017	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	6647000	USD
CY2015	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	4433000	USD
CY2016	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	2719000	USD
CY2017	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	2963000	USD
CY2015	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	6825000	USD
CY2016	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	72215000	USD
CY2017	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	4967000	USD
CY2015	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	33717000	USD
CY2016	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	16721000	USD
CY2017	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-10578000	USD
CY2016Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	112330000	USD
CY2017Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	106395000	USD
CY2015Q3	us-gaap	Assets Assets	6564939000	USD
CY2016Q3	us-gaap	Assets Assets	5636387000	USD
CY2017Q3	us-gaap	Assets Assets	6103320000	USD
CY2016Q3	us-gaap	Assets Current AssetsCurrent	413031000	USD
CY2017Q3	us-gaap	Assets Current AssetsCurrent	818280000	USD
CY2016Q3	us-gaap	Assets Noncurrent AssetsNoncurrent	768874000	USD
CY2017Q3	us-gaap	Assets Noncurrent AssetsNoncurrent	610966000	USD
CY2015	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	118959000	USD
CY2016	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	60434000	USD
CY2017	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	72216000	USD
CY2016Q3	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	3613256000	USD
CY2017Q3	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	3787416000	USD
CY2016Q3	us-gaap	Capitalized Costs Accumulated Depreciation Depletion Amortization And Valuation Allowance For Relating To Oil And Gas Producing Activities CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities	3657239000	USD
CY2017Q3	us-gaap	Capitalized Costs Accumulated Depreciation Depletion Amortization And Valuation Allowance For Relating To Oil And Gas Producing Activities CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities	3765710000	USD
CY2016Q3	us-gaap	Capitalized Costs Asset Retirement Costs CapitalizedCostsAssetRetirementCosts	63600000	USD
CY2017Q3	us-gaap	Capitalized Costs Asset Retirement Costs CapitalizedCostsAssetRetirementCosts	54400000	USD
CY2015	us-gaap	Capitalized Costs Of Unproved Properties Excluded From Amortization CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization	3923000	USD
CY2016	us-gaap	Capitalized Costs Of Unproved Properties Excluded From Amortization CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization	14449000	USD
CY2017	us-gaap	Capitalized Costs Of Unproved Properties Excluded From Amortization CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization	6999000	USD
CY2016Q3	us-gaap	Capitalized Costs Oil And Gas Producing Activities Gross CapitalizedCostsOilAndGasProducingActivitiesGross	4690214000	USD
CY2017Q3	us-gaap	Capitalized Costs Oil And Gas Producing Activities Gross CapitalizedCostsOilAndGasProducingActivitiesGross	4913233000	USD
CY2016Q3	us-gaap	Capitalized Costs Oil And Gas Producing Activities Net CapitalizedCostsOilAndGasProducingActivitiesNet	1032975000	USD
CY2017Q3	us-gaap	Capitalized Costs Oil And Gas Producing Activities Net CapitalizedCostsOilAndGasProducingActivitiesNet	1147523000	USD
CY2016Q3	us-gaap	Capitalized Costs Proved Properties CapitalizedCostsProvedProperties	4554929000	USD
CY2017Q3	us-gaap	Capitalized Costs Proved Properties CapitalizedCostsProvedProperties	4832301000	USD
CY2016Q3	us-gaap	Capitalized Costs Unproved Properties CapitalizedCostsUnprovedProperties	135285000	USD
CY2017Q3	us-gaap	Capitalized Costs Unproved Properties CapitalizedCostsUnprovedProperties	80932000	USD
CY2014Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	36886000	USD
CY2015Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	113596000	USD
CY2016Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	129972000	USD
CY2017Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	555530000	USD
CY2016Q3	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	113407000	USD
CY2017Q3	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	527978000	USD
CY2015	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	76710000	USD
CY2016	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	16376000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	425558000	USD
CY2017	us-gaap	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths	18000000	USD
CY2016Q3	us-gaap	Cash Surrender Value Of Life Insurance CashSurrenderValueOfLifeInsurance	39700000	USD
CY2017Q3	us-gaap	Cash Surrender Value Of Life Insurance CashSurrenderValueOfLifeInsurance	39400000	USD
CY2016Q3	us-gaap	Commercial Paper At Carrying Value CommercialPaperAtCarryingValue	0	USD
CY2017Q3	us-gaap	Commercial Paper At Carrying Value CommercialPaperAtCarryingValue	0	USD
CY2016Q3	us-gaap	Commitments And Contingencies CommitmentsAndContingencies	0	USD
CY2017Q3	us-gaap	Commitments And Contingencies CommitmentsAndContingencies	0	USD
CY2015	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.56
CY2016	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.60
CY2017	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.64
CY2015Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.395
CY2016Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.395
CY2016Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.405
CY2016Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.405
CY2016Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.405
CY2017Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.405
CY2017Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.415
CY2017Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.415
CY2016Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1
CY2017Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1
CY2016Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2017Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2016Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	85118886	shares
CY2017Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	85543125	shares
CY2016Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	85118886	shares
CY2017Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	85543125	shares
CY2016Q3	us-gaap	Common Stock Value CommonStockValue	85119000	USD
CY2017Q3	us-gaap	Common Stock Value CommonStockValue	85543000	USD
CY2015	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	-282076000	USD
CY2016	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	-389970000	USD
CY2015	us-gaap	Costs Incurred Development Costs CostsIncurredDevelopmentCosts	454605000	USD
CY2016	us-gaap	Costs Incurred Development Costs CostsIncurredDevelopmentCosts	219386000	USD
CY2017	us-gaap	Costs Incurred Development Costs CostsIncurredDevelopmentCosts	200639000	USD
CY2015	us-gaap	Costs Incurred Exploration Costs CostsIncurredExplorationCosts	53222000	USD
CY2016	us-gaap	Costs Incurred Exploration Costs CostsIncurredExplorationCosts	27561000	USD
CY2017	us-gaap	Costs Incurred Exploration Costs CostsIncurredExplorationCosts	40975000	USD
CY2017Q3	us-gaap	Credit Risk Derivative Assets At Fair Value CreditRiskDerivativeAssetsAtFairValue	26000000	USD
CY2016Q3	us-gaap	Debt Instrument Unamortized Discount Premium And Debt Issuance Costs Net DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	12748000	USD
CY2017Q3	us-gaap	Debt Instrument Unamortized Discount Premium And Debt Issuance Costs Net DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	15319000	USD
CY2017Q3	us-gaap	Debt Instrument Unused Borrowing Capacity Amount DebtInstrumentUnusedBorrowingCapacityAmount	1150000000	USD
CY2015	us-gaap	Decrease Due To Sales Of Minerals In Place DecreaseDueToSalesOfMineralsInPlace	1000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	258999000	USD
CY2015	us-gaap	Cost Of Purchased Oil And Gas CostOfPurchasedOilAndGas	349984000	USD
CY2016	us-gaap	Cost Of Purchased Oil And Gas CostOfPurchasedOilAndGas	147982000	USD
CY2017	us-gaap	Cost Of Purchased Oil And Gas CostOfPurchasedOilAndGas	275254000	USD
CY2015	us-gaap	Costs Incurred Acquisition Of Oil And Gas Properties CostsIncurredAcquisitionOfOilAndGasProperties	567187000	USD
CY2016	us-gaap	Costs Incurred Acquisition Of Oil And Gas Properties CostsIncurredAcquisitionOfOilAndGasProperties	200801000	USD
CY2017	us-gaap	Costs Incurred Acquisition Of Oil And Gas Properties CostsIncurredAcquisitionOfOilAndGasProperties	241609000	USD
CY2015	us-gaap	Costs Incurred Acquisition Of Oil And Gas Properties With Proved Reserves CostsIncurredAcquisitionOfOilAndGasPropertiesWithProvedReserves	1767000	USD
CY2016	us-gaap	Costs Incurred Acquisition Of Oil And Gas Properties With Proved Reserves CostsIncurredAcquisitionOfOilAndGasPropertiesWithProvedReserves	1342000	USD
CY2017	us-gaap	Costs Incurred Acquisition Of Oil And Gas Properties With Proved Reserves CostsIncurredAcquisitionOfOilAndGasPropertiesWithProvedReserves	8908000	USD
CY2015	us-gaap	Costs Incurred Acquisition Of Unproved Oil And Gas Properties CostsIncurredAcquisitionOfUnprovedOilAndGasProperties	19998000	USD
CY2016	us-gaap	Costs Incurred Acquisition Of Unproved Oil And Gas Properties CostsIncurredAcquisitionOfUnprovedOilAndGasProperties	2165000	USD
CY2017	us-gaap	Costs Incurred Acquisition Of Unproved Oil And Gas Properties CostsIncurredAcquisitionOfUnprovedOilAndGasProperties	262000	USD
CY2015	us-gaap	Costs Incurred Asset Retirement Obligation Incurred CostsIncurredAssetRetirementObligationIncurred	37595000	USD
CY2016	us-gaap	Costs Incurred Asset Retirement Obligation Incurred CostsIncurredAssetRetirementObligationIncurred	-49653000	USD
CY2017	us-gaap	Costs Incurred Asset Retirement Obligation Incurred CostsIncurredAssetRetirementObligationIncurred	-9175000	USD
CY2017Q3	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	31900000	USD
CY2017Q3	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	31900000	USD
CY2015	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	25064000	USD
CY2016	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-6658000	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	32034000	USD
CY2015	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	13387000	USD
CY2016	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	20903000	USD
CY2017	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	10673000	USD
CY2016Q3	us-gaap	Customer Advances Current CustomerAdvancesCurrent	14762000	USD
CY2017Q3	us-gaap	Customer Advances Current CustomerAdvancesCurrent	15701000	USD
CY2016Q3	us-gaap	Customer Deposits Current CustomerDepositsCurrent	16019000	USD
CY2017Q3	us-gaap	Customer Deposits Current CustomerDepositsCurrent	20372000	USD
CY2016Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	2086252000	USD
CY2017Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	2383681000	USD
CY2016Q3	us-gaap	Debt Instrument Fair Value DebtInstrumentFairValue	2255562000	USD
CY2017Q3	us-gaap	Debt Instrument Fair Value DebtInstrumentFairValue	2523639000	USD
CY2017Q3	us-gaap	Debt Instrument Repurchase Amount DebtInstrumentRepurchaseAmount	307000000	USD
CY2017	us-gaap	Decrease Due To Sales Of Minerals In Place DecreaseDueToSalesOfMineralsInPlace	9849000	USD
CY2016Q3	us-gaap	Deferred Costs DeferredCosts	20978000	USD
CY2016	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-164818000	USD
CY2016	us-gaap	Decrease Due To Sales Of Minerals In Place DecreaseDueToSalesOfMineralsInPlace	95849000	USD
CY2017Q3	us-gaap	Deferred Costs DeferredCosts	30047000	USD
CY2015	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-244336000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Derivatives DeferredTaxLiabilitiesDerivatives	50179000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Derivatives DeferredTaxLiabilitiesDerivatives	19127000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	823795000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	103046000	USD
CY2015	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-357587000	USD
CY2016	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-246794000	USD
CY2017	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	117975000	USD
CY2015	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-113251000	USD
CY2016	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-81976000	USD
CY2017	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	14929000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Capital Loss Carryforwards DeferredTaxAssetsCapitalLossCarryforwards	194875000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Capital Loss Carryforwards DeferredTaxAssetsCapitalLossCarryforwards	200344000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	-823795000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	-891287000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	482844000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	406707000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	92140000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	82831000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1306639000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1297994000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	891287000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	55457000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	57919000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	1049100000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	1141432000	USD
CY2016Q3	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Prior Service Cost Credit After Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditAfterTax	1300000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Prior Service Cost Credit After Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditAfterTax	1200000	USD
CY2016Q3	us-gaap	Defined Benefit Plan Assets For Plan Benefits Noncurrent DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent	17649000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Assets For Plan Benefits Noncurrent DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent	56370000	USD
CY2017	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Decrease On Accumulated Postretirement Benefit Obligation1 DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1	48500000	USD
CY2017	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Decrease On Service And Interest Cost Components1 DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1	2700000	USD
CY2017	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Increase On Accumulated Postretirement Benefit Obligation DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation	57900000	USD
CY2017	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Increase On Service And Interest Cost Components DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents	3300000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	331100000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	64400000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	66200000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	65800000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	65400000	USD
CY2017Q3	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	65000000	USD
CY2015Q3	us-gaap	Defined Benefit Plan Ultimate Health Care Cost Trend Rate1 DefinedBenefitPlanUltimateHealthCareCostTrendRate1	0.045
CY2016Q3	us-gaap	Defined Benefit Plan Ultimate Health Care Cost Trend Rate1 DefinedBenefitPlanUltimateHealthCareCostTrendRate1	0.045
CY2017Q3	us-gaap	Defined Benefit Plan Ultimate Health Care Cost Trend Rate1 DefinedBenefitPlanUltimateHealthCareCostTrendRate1	0.045
CY2015	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	336158000	USD
CY2016	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	249417000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	224195000	USD
CY2016Q3	us-gaap	Derivative Instruments And Hedges Liabilities DerivativeInstrumentsAndHedgesLiabilities	1560000	USD
CY2017Q3	us-gaap	Derivative Instruments And Hedges Liabilities DerivativeInstrumentsAndHedgesLiabilities	1103000	USD
CY2016Q3	us-gaap	Derivative Instruments And Hedges Noncurrent DerivativeInstrumentsAndHedgesNoncurrent	113804000	USD
CY2017Q3	us-gaap	Derivative Instruments And Hedges Noncurrent DerivativeInstrumentsAndHedgesNoncurrent	36111000	USD
CY2016	us-gaap	Derivative Instruments Gain Loss Reclassified From Accumulated Oci Into Income Effective Portion Net DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet	220919000	USD
CY2017	us-gaap	Derivative Instruments Gain Loss Reclassified From Accumulated Oci Into Income Effective Portion Net DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet	81605000	USD
CY2016	us-gaap	Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet	392000	USD
CY2017	us-gaap	Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet	-100000	USD
CY2015	us-gaap	Development Costs DevelopmentCosts	416000	USD
CY2016	us-gaap	Development Costs DevelopmentCosts	6707000	USD
CY2017	us-gaap	Development Costs DevelopmentCosts	4388000	USD
CY2015	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	131734000	USD
CY2016	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	135881000	USD
CY2017	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	140090000	USD
CY2016Q3	us-gaap	Dividends Payable Current DividendsPayableCurrent	34473000	USD
CY2017Q3	us-gaap	Dividends Payable Current DividendsPayableCurrent	35500000	USD
CY2015	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-4.50
CY2015Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-2.23
CY2016Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-1.74
CY2016Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.10
CY2016Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.44
CY2016	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-3.43
CY2016Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.04
CY2017Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.05
CY2017Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.70
CY2017Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.53
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.32
CY2015	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-4.50
CY2015Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-2.23
CY2016Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-1.74
CY2016Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.10
CY2016Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.44
CY2016	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-3.43
CY2016Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.04
CY2017Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.04
CY2017Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.69
CY2017Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.53
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.30
CY2015	us-gaap	Effect On Future Cash Flows Amount EffectOnFutureCashFlowsAmount	194500000	USD
CY2016	us-gaap	Effect On Future Cash Flows Amount EffectOnFutureCashFlowsAmount	215300000	USD
CY2017	us-gaap	Effect On Future Cash Flows Amount EffectOnFutureCashFlowsAmount	30500000	USD
CY2015	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2016	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2015	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	100000	USD
CY2016	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	100000	USD
CY2017	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	100000	USD
CY2015	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	900000	USD
CY2016	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	1900000	USD
CY2017	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	4400000	USD
CY2017	us-gaap	Employee Service Share Based Compensation Tax Benefit From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions	500000	USD
CY2016Q3	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	34332000	USD
CY2017Q3	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	35689000	USD
CY2015	us-gaap	Excess Tax Benefit From Share Based Compensation Financing Activities ExcessTaxBenefitFromShareBasedCompensationFinancingActivities	9064000	USD
CY2016	us-gaap	Excess Tax Benefit From Share Based Compensation Financing Activities ExcessTaxBenefitFromShareBasedCompensationFinancingActivities	1868000	USD
CY2017	us-gaap	Excess Tax Benefit From Share Based Compensation Financing Activities ExcessTaxBenefitFromShareBasedCompensationFinancingActivities	0	USD
CY2015	us-gaap	Excess Tax Benefit From Share Based Compensation Operating Activities ExcessTaxBenefitFromShareBasedCompensationOperatingActivities	9064000	USD
CY2016	us-gaap	Excess Tax Benefit From Share Based Compensation Operating Activities ExcessTaxBenefitFromShareBasedCompensationOperatingActivities	1868000	USD
CY2017	us-gaap	Excess Tax Benefit From Share Based Compensation Operating Activities ExcessTaxBenefitFromShareBasedCompensationOperatingActivities	0	USD
CY2015	us-gaap	Exploration Costs ExplorationCosts	3419000	USD
CY2016	us-gaap	Exploration Costs ExplorationCosts	7593000	USD
CY2017	us-gaap	Exploration Costs ExplorationCosts	2376000	USD
CY2015	us-gaap	Extensions Discoveries Additions And Improved Recovery Less Related Costs ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts	266159000	USD
CY2016	us-gaap	Extensions Discoveries Additions And Improved Recovery Less Related Costs ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts	47742000	USD
CY2017	us-gaap	Extensions Discoveries Additions And Improved Recovery Less Related Costs ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts	170500000	USD
CY2016Q3	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0	USD
CY2017Q3	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0	USD
CY2016	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Net FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet	0	USD
CY2017	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Net FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet	0	USD
CY2015Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Cash Inflows FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows	6916775000	USD
CY2016Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Cash Inflows FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows	3768463000	USD
CY2017Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Cash Inflows FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows	6144317000	USD
CY2015Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Development Costs FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts	761922000	USD
CY2016Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Development Costs FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts	375152000	USD
CY2017Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Development Costs FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts	411578000	USD
CY2015Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Income Tax Expense FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense	1117433000	USD
CY2016Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Income Tax Expense FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense	303397000	USD
CY2017Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Income Tax Expense FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense	1160469000	USD
CY2015Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Net Cash Flows FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows	2183278000	USD
CY2016Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Net Cash Flows FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows	1094998000	USD
CY2017Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Net Cash Flows FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows	2194008000	USD
CY2015Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Production Costs FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts	2854142000	USD
CY2016Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Production Costs FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts	1994916000	USD
CY2017Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Production Costs FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts	2378262000	USD
CY2015Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Ten Percent Annual Discount For Estimated Timing Of Cash Flows FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows	860244000	USD
CY2016Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Ten Percent Annual Discount For Estimated Timing Of Cash Flows FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows	452470000	USD
CY2017Q3	us-gaap	Future Net Cash Flows Relating To Proved Oil And Gas Reserves Ten Percent Annual Discount For Estimated Timing Of Cash Flows FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows	1080962000	USD
CY2017	us-gaap	Gain Loss On Fair Value Hedges Recognized In Earnings GainLossOnFairValueHedgesRecognizedInEarnings	2119000	USD
CY2016Q3	us-gaap	Goodwill Goodwill	5476000	USD
CY2017Q3	us-gaap	Goodwill Goodwill	5476000	USD
CY2017Q3	us-gaap	Goodwill Goodwill	5500000	USD
CY2015	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-698563000	USD
CY2016	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-523507000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	444164000	USD
CY2015	us-gaap	Income Tax Effects Allocated Directly To Equity Cumulative Effect Of Change In Accounting Principle IncomeTaxEffectsAllocatedDirectlyToEquityCumulativeEffectOfChangeInAccountingPrinciple	0	USD
CY2016	us-gaap	Income Tax Effects Allocated Directly To Equity Cumulative Effect Of Change In Accounting Principle IncomeTaxEffectsAllocatedDirectlyToEquityCumulativeEffectOfChangeInAccountingPrinciple	0	USD
CY2017	us-gaap	Income Tax Effects Allocated Directly To Equity Cumulative Effect Of Change In Accounting Principle IncomeTaxEffectsAllocatedDirectlyToEquityCumulativeEffectOfChangeInAccountingPrinciple	31916000	USD
CY2015	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-319136000	USD
CY2016	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-232549000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	160682000	USD
CY2015	us-gaap	Income Tax Reconciliation Deductions Other IncomeTaxReconciliationDeductionsOther	9264000	USD
CY2015	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	23173000	USD
CY2016	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-13483000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	2183000	USD
CY2015	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	-51638000	USD
CY2016	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	-183349000	USD
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	155397000	USD
CY2015	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	-64912000	USD
CY2016	us-gaap	Income Tax Reconciliation Deductions Other IncomeTaxReconciliationDeductionsOther	6589000	USD
CY2017	us-gaap	Income Tax Reconciliation Deductions Other IncomeTaxReconciliationDeductionsOther	4850000	USD
CY2015	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	-244642000	USD
CY2016	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	-39697000	USD
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	16641000	USD
CY2015	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	732000	USD
CY2016	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	3262000	USD
CY2017	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	6679000	USD
CY2015	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	18657000	USD
CY2016	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	34240000	USD
CY2017	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	34826000	USD
CY2015	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	34687000	USD
CY2016	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	-40664000	USD
CY2017	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	17192000	USD
CY2015	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	-7173000	USD
CY2016	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	3453000	USD
CY2017	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	27004000	USD
CY2015	us-gaap	Increase Decrease In Customer Advances IncreaseDecreaseInCustomerAdvances	-2769000	USD
CY2016	us-gaap	Increase Decrease In Customer Advances IncreaseDecreaseInCustomerAdvances	-1474000	USD
CY2017	us-gaap	Increase Decrease In Customer Advances IncreaseDecreaseInCustomerAdvances	939000	USD
CY2015	us-gaap	Increase Decrease In Customer Deposits IncreaseDecreaseInCustomerDeposits	729000	USD
CY2016	us-gaap	Increase Decrease In Customer Deposits IncreaseDecreaseInCustomerDeposits	-471000	USD
CY2017	us-gaap	Increase Decrease In Customer Deposits IncreaseDecreaseInCustomerDeposits	4353000	USD
CY2015	us-gaap	Increase Decrease In Deferred Gas Cost IncreaseDecreaseInDeferredGasCost	0	USD
CY2016	us-gaap	Increase Decrease In Deferred Gas Cost IncreaseDecreaseInDeferredGasCost	2440000	USD
CY2017	us-gaap	Increase Decrease In Deferred Gas Cost IncreaseDecreaseInDeferredGasCost	2183000	USD
CY2015	us-gaap	Increase Decrease In Estimated Future Development Costs IncreaseDecreaseInEstimatedFutureDevelopmentCosts	164510000	USD
CY2016	us-gaap	Increase Decrease In Estimated Future Development Costs IncreaseDecreaseInEstimatedFutureDevelopmentCosts	143752000	USD
CY2017	us-gaap	Increase Decrease In Estimated Future Development Costs IncreaseDecreaseInEstimatedFutureDevelopmentCosts	8816000	USD
CY2015	us-gaap	Increase Decrease In Future Income Tax Expense Estimates On Future Cash Flows Related To Proved Oil And Gas Reserves IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves	545442000	USD
CY2016	us-gaap	Increase Decrease In Future Income Tax Expense Estimates On Future Cash Flows Related To Proved Oil And Gas Reserves IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves	387739000	USD
CY2017	us-gaap	Increase Decrease In Future Income Tax Expense Estimates On Future Cash Flows Related To Proved Oil And Gas Reserves IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves	-393353000	USD
CY2015	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-3438000	USD
CY2016	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	3532000	USD
CY2017	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	1417000	USD
CY2015	us-gaap	Increase Decrease In Margin Deposits Outstanding IncreaseDecreaseInMarginDepositsOutstanding	8390000	USD
CY2016	us-gaap	Increase Decrease In Margin Deposits Outstanding IncreaseDecreaseInMarginDepositsOutstanding	-9640000	USD
CY2017	us-gaap	Increase Decrease In Margin Deposits Outstanding IncreaseDecreaseInMarginDepositsOutstanding	257000	USD
CY2015	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	-3150000	USD
CY2016	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	-3179000	USD
CY2017	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	-7849000	USD
CY2015	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-2696000	USD
CY2016	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-1941000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	2885000	USD
CY2016	us-gaap	Increase Decrease In Regulatory Clause Revenue IncreaseDecreaseInRegulatoryClauseRevenue	-37241000	USD
CY2017Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	6103320000	USD
CY2016Q3	us-gaap	Liabilities Current LiabilitiesCurrent	303737000	USD
CY2016	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	6408000	USD
CY2017	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	3380000	USD
CY2015	us-gaap	Increase Decrease In Regulatory Clause Revenue IncreaseDecreaseInRegulatoryClauseRevenue	23033000	USD
CY2017	us-gaap	Increase Decrease In Regulatory Clause Revenue IncreaseDecreaseInRegulatoryClauseRevenue	-19537000	USD
CY2015	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	88000	USD
CY2016	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	149000	USD
CY2017	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	235000	USD
CY2015	us-gaap	Interest Expense InterestExpense	99471000	USD
CY2016	us-gaap	Interest Expense InterestExpense	121044000	USD
CY2017	us-gaap	Interest Expense InterestExpense	119837000	USD
CY2015	us-gaap	Interest Expense Long Term Debt InterestExpenseLongTermDebt	95916000	USD
CY2016	us-gaap	Interest Expense Long Term Debt InterestExpenseLongTermDebt	117347000	USD
CY2017	us-gaap	Interest Expense Long Term Debt InterestExpenseLongTermDebt	116471000	USD
CY2015	us-gaap	Interest Expense Other InterestExpenseOther	3555000	USD
CY2016	us-gaap	Interest Expense Other InterestExpenseOther	3697000	USD
CY2017	us-gaap	Interest Expense Other InterestExpenseOther	3366000	USD
CY2015	us-gaap	Interest Income Domestic Deposits InterestIncomeDomesticDeposits	3922000	USD
CY2016	us-gaap	Interest Income Domestic Deposits InterestIncomeDomesticDeposits	4235000	USD
CY2017	us-gaap	Interest Income Domestic Deposits InterestIncomeDomesticDeposits	4113000	USD
CY2015	us-gaap	Interest Paid InterestPaid	90747000	USD
CY2016	us-gaap	Interest Paid InterestPaid	119563000	USD
CY2017	us-gaap	Interest Paid InterestPaid	116894000	USD
CY2016Q3	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	33866000	USD
CY2017Q3	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	33926000	USD
CY2015	us-gaap	Investment Tax Credit InvestmentTaxCredit	-414000	USD
CY2016	us-gaap	Investment Tax Credit InvestmentTaxCredit	-348000	USD
CY2017	us-gaap	Investment Tax Credit InvestmentTaxCredit	-173000	USD
CY2016Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	5636387000	USD
CY2017Q3	us-gaap	Liabilities Current LiabilitiesCurrent	646039000	USD
CY2016Q3	us-gaap	Liabilities Noncurrent LiabilitiesNoncurrent	1719394000	USD
CY2017Q3	us-gaap	Liabilities Noncurrent LiabilitiesNoncurrent	1669865000	USD
CY2017Q3	us-gaap	Line Of Credit LineOfCredit	0	USD
CY2016Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	0	USD
CY2017Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	300000000	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	1349000000	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	300000000	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	500000000	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	0	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	250000000	USD
CY2016Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2086252000	USD
CY2017Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2083681000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	3700000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	4600000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	1900000	USD
CY2016Q3	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	74430000	USD
CY2017Q3	us-gaap	Loss Contingency Estimate Of Possible Loss LossContingencyEstimateOfPossibleLoss	3100000	USD
CY2016Q3	us-gaap	Margin Deposit Assets MarginDepositAssets	1484000	USD
CY2017Q3	us-gaap	Margin Deposit Assets MarginDepositAssets	1741000	USD
CY2015	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	247920000	USD
CY2016	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	-119107000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	163872000	USD
CY2015	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-1024790000	USD
CY2016	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-453496000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-422565000	USD
CY2015	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	853580000	USD
CY2016	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	588979000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	684251000	USD
CY2015	us-gaap	Net Income Loss NetIncomeLoss	-379427000	USD
CY2015Q4	us-gaap	Net Income Loss NetIncomeLoss	-189109000	USD
CY2016Q1	us-gaap	Net Income Loss NetIncomeLoss	-147688000	USD
CY2016Q2	us-gaap	Net Income Loss NetIncomeLoss	8286000	USD
CY2016Q3	us-gaap	Net Income Loss NetIncomeLoss	37553000	USD
CY2016	us-gaap	Net Income Loss NetIncomeLoss	-290958000	USD
CY2016Q4	us-gaap	Net Income Loss NetIncomeLoss	88908000	USD
CY2017Q1	us-gaap	Net Income Loss NetIncomeLoss	89283000	USD
CY2017Q2	us-gaap	Net Income Loss NetIncomeLoss	59714000	USD
CY2017Q3	us-gaap	Net Income Loss NetIncomeLoss	45577000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	283482000	USD
CY2015	us-gaap	Net Increase Decrease In Sales And Transfer Prices And Production Costs NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts	-1752843000	USD
CY2016	us-gaap	Net Increase Decrease In Sales And Transfer Prices And Production Costs NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts	-1066593000	USD
CY2017	us-gaap	Net Increase Decrease In Sales And Transfer Prices And Production Costs NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts	828187000	USD
CY2017	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	5
CY2015	us-gaap	Operating Expenses OperatingExpenses	2371966000	USD
CY2016	us-gaap	Operating Expenses OperatingExpenses	1868934000	USD
CY2017	us-gaap	Operating Expenses OperatingExpenses	1027036000	USD
CY2015	us-gaap	Operating Income Loss OperatingIncomeLoss	-611053000	USD
CY2015Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	-305924000	USD
CY2016Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	-237000000	USD
CY2016Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	45162000	USD
CY2016Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	81244000	USD
CY2016	us-gaap	Operating Income Loss OperatingIncomeLoss	-416518000	USD
CY2016Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	172139000	USD
CY2017Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	169957000	USD
CY2017Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	123354000	USD
CY2017Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	87395000	USD
CY2017	us-gaap	Operating Income Loss OperatingIncomeLoss	552845000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	10800000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	1500000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	2200000	USD
CY2017Q3	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	111889000	USD
CY2016Q3	us-gaap	Other Assets Current OtherAssetsCurrent	59354000	USD
CY2017Q3	us-gaap	Other Assets Current OtherAssetsCurrent	51505000	USD
CY2016Q3	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	604000	USD
CY2017Q3	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	742000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	29750000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	15327000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	169919000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-171586000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-44731000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	97351000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-99012000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-24483000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Reclassification Adjustments And Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax	31538000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Reclassification Adjustments And Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax	21378000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Reclassification Adjustments And Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax	-15661000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Before Reclassification Adjustments Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax	11922000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Before Reclassification Adjustments Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax	8351000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Before Reclassification Adjustments Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax	-6175000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	591000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	1374000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	1575000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	217000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	527000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	580000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	184953000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	220919000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	81605000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax	78345000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax	86659000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax	34286000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax	9217000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax	10068000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax	13433000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	3375000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	3723000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	4929000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	72568000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-72574000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-20248000	USD
CY2015	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	381018000	USD
CY2016	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	60493000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	5347000	USD
CY2015	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	160872000	USD
CY2016	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	18648000	USD
CY2016Q3	us-gaap	Prepaid Taxes PrepaidTaxes	13138000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	2009000	USD
CY2015	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-3234000	USD
CY2016	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	1524000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	4008000	USD
CY2015	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-1195000	USD
CY2016	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	592000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	1505000	USD
CY2016Q3	us-gaap	Other Deferred Credits Noncurrent OtherDeferredCreditsNoncurrent	119625000	USD
CY2017Q3	us-gaap	Other Deferred Credits Noncurrent OtherDeferredCreditsNoncurrent	109019000	USD
CY2015	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-9823000	USD
CY2016	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-12620000	USD
CY2017	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-16476000	USD
CY2015	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	8039000	USD
CY2016	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	9820000	USD
CY2017	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	7043000	USD
CY2016Q3	us-gaap	Other Prepaid Expense Current OtherPrepaidExpenseCurrent	10919000	USD
CY2017Q3	us-gaap	Other Prepaid Expense Current OtherPrepaidExpenseCurrent	10927000	USD
CY2015	us-gaap	Other Significant Noncash Transaction Value Of Consideration Received1 OtherSignificantNoncashTransactionValueOfConsiderationReceived1	0	USD
CY2016	us-gaap	Other Significant Noncash Transaction Value Of Consideration Received1 OtherSignificantNoncashTransactionValueOfConsiderationReceived1	19543000	USD
CY2017	us-gaap	Other Significant Noncash Transaction Value Of Consideration Received1 OtherSignificantNoncashTransactionValueOfConsiderationReceived1	0	USD
CY2015	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	6611000	USD
CY2016	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	9236000	USD
CY2017	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-1216000	USD
CY2015	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	130719000	USD
CY2016	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	134824000	USD
CY2017	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	139063000	USD
CY2015	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1018179000	USD
CY2016	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	581576000	USD
CY2017	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	450335000	USD
CY2016Q3	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent	277113000	USD
CY2017Q3	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent	149079000	USD
CY2017Q3	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	1
CY2017Q3	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	10000000	shares
CY2017Q3	us-gaap	Prepaid Taxes PrepaidTaxes	13974000	USD
CY2015	us-gaap	Previously Estimated Development Costs Incurred PreviouslyEstimatedDevelopmentCostsIncurred	161833000	USD
CY2016	us-gaap	Previously Estimated Development Costs Incurred PreviouslyEstimatedDevelopmentCostsIncurred	92840000	USD
CY2017	us-gaap	Previously Estimated Development Costs Incurred PreviouslyEstimatedDevelopmentCostsIncurred	101134000	USD
CY2015	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	444635000	USD
CY2016	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
CY2017	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	295151000	USD
CY2015	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-85600000	USD
CY2016	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	0	USD
CY2017	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	0	USD
CY2015	us-gaap	Proceeds From Repurchase Of Equity ProceedsFromRepurchaseOfEquity	10540000	USD
CY2016	us-gaap	Proceeds From Repurchase Of Equity ProceedsFromRepurchaseOfEquity	13849000	USD
CY2017	us-gaap	Proceeds From Repurchase Of Equity ProceedsFromRepurchaseOfEquity	7784000	USD
CY2015	us-gaap	Proceeds From Sale Of Oil And Gas Property And Equipment ProceedsFromSaleOfOilAndGasPropertyAndEquipment	0	USD
CY2016	us-gaap	Proceeds From Sale Of Oil And Gas Property And Equipment ProceedsFromSaleOfOilAndGasPropertyAndEquipment	137316000	USD
CY2017	us-gaap	Proceeds From Sale Of Oil And Gas Property And Equipment ProceedsFromSaleOfOilAndGasPropertyAndEquipment	26554000	USD
CY2015	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	1000509000	USD
CY2016	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	523051000	USD
CY2017	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	462117000	USD
CY2016Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	9539581000	USD
CY2017Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	9945560000	USD
CY2016Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	4454482000	USD
CY2017Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	4674074000	USD
CY2015Q3	us-gaap	Proved Undeveloped Reserve Volume ProvedUndevelopedReserveVolume	827000000000	ft3
CY2016Q3	us-gaap	Proved Undeveloped Reserve Volume ProvedUndevelopedReserveVolume	543000000000	ft3
CY2017Q3	us-gaap	Proved Undeveloped Reserve Volume ProvedUndevelopedReserveVolume	612000000000	ft3
CY2017	us-gaap	Public Utilities Approved Equity Capital Structure Percentage PublicUtilitiesApprovedEquityCapitalStructurePercentage	0.429
CY2017	us-gaap	Public Utilities Approved Rate Increase Decrease Amount PublicUtilitiesApprovedRateIncreaseDecreaseAmount	5900000	USD
CY2017	us-gaap	Public Utilities Approved Return On Equity Percentage PublicUtilitiesApprovedReturnOnEquityPercentage	0.087
CY2017	us-gaap	Public Utilities Requested Rate Increase Decrease Amount PublicUtilitiesRequestedRateIncreaseDecreaseAmount	41700000	USD
CY2016Q3	us-gaap	Receivables Net Current ReceivablesNetCurrent	133201000	USD
CY2017Q3	us-gaap	Receivables Net Current ReceivablesNetCurrent	112383000	USD
CY2016	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	128762000	USD
CY2017	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	39810000	USD
CY2017Q3	us-gaap	Recorded Unconditional Purchase Obligation Due After Fifth Year RecordedUnconditionalPurchaseObligationDueAfterFifthYear	504900000	USD
CY2017Q3	us-gaap	Recorded Unconditional Purchase Obligation Due In Fifth Year RecordedUnconditionalPurchaseObligationDueInFifthYear	61700000	USD
CY2017Q3	us-gaap	Recorded Unconditional Purchase Obligation Due In Fourth Year RecordedUnconditionalPurchaseObligationDueInFourthYear	70900000	USD
CY2017Q3	us-gaap	Recorded Unconditional Purchase Obligation Due In Second Year RecordedUnconditionalPurchaseObligationDueInSecondYear	84600000	USD
CY2017Q3	us-gaap	Recorded Unconditional Purchase Obligation Due In Third Year RecordedUnconditionalPurchaseObligationDueInThirdYear	77900000	USD
CY2017Q3	us-gaap	Recorded Unconditional Purchase Obligation Due Within One Year RecordedUnconditionalPurchaseObligationDueWithinOneYear	262400000	USD
CY2016Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	19537000	USD
CY2017Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	0	USD
CY2016Q3	us-gaap	Regulatory Assets RegulatoryAssets	515315000	USD
CY2017Q3	us-gaap	Regulatory Assets RegulatoryAssets	372839000	USD
CY2016Q3	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	15616000	USD
CY2017Q3	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	15884000	USD
CY2016Q3	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	320750000	USD
CY2017Q3	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	174433000	USD
CY2016Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	420793000	USD
CY2017Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	448144000	USD
CY2016Q3	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	34262000	USD
CY2017Q3	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	34059000	USD
CY2016Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	99789000	USD
CY2017Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	113716000	USD
CY2015	us-gaap	Results Of Operations Accretion Of Asset Retirement Obligations ResultsOfOperationsAccretionOfAssetRetirementObligations	6186000	USD
CY2017	us-gaap	Results Of Operations Accretion Of Asset Retirement Obligations ResultsOfOperationsAccretionOfAssetRetirementObligations	4896000	USD
CY2015	us-gaap	Results Of Operations Depreciation Depletion And Amortization And Valuation Provisions ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions	234480000	USD
CY2016	us-gaap	Results Of Operations Depreciation Depletion And Amortization And Valuation Provisions ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions	136579000	USD
CY2017	us-gaap	Results Of Operations Depreciation Depletion And Amortization And Valuation Provisions ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions	108471000	USD
CY2016	us-gaap	Results Of Operations Accretion Of Asset Retirement Obligations ResultsOfOperationsAccretionOfAssetRetirementObligations	6663000	USD
CY2015	us-gaap	Results Of Operations Impairment Of Oil And Gas Properties ResultsOfOperationsImpairmentOfOilAndGasProperties	1126257000	USD
CY2016	us-gaap	Results Of Operations Impairment Of Oil And Gas Properties ResultsOfOperationsImpairmentOfOilAndGasProperties	948307000	USD
CY2017	us-gaap	Results Of Operations Impairment Of Oil And Gas Properties ResultsOfOperationsImpairmentOfOilAndGasProperties	0	USD
CY2015	us-gaap	Results Of Operations Income Tax Expense ResultsOfOperationsIncomeTaxExpense	-444393000	USD
CY2016	us-gaap	Results Of Operations Income Tax Expense ResultsOfOperationsIncomeTaxExpense	-368940000	USD
CY2017	us-gaap	Results Of Operations Income Tax Expense ResultsOfOperationsIncomeTaxExpense	86657000	USD
CY2015	us-gaap	Results Of Operations Oil And Gas Producing Activities Net Income Excluding Corporate Overhead And Interest Costs ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts	-606865000	USD
CY2016	us-gaap	Results Of Operations Oil And Gas Producing Activities Net Income Excluding Corporate Overhead And Interest Costs ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts	-504865000	USD
CY2017	us-gaap	Results Of Operations Oil And Gas Producing Activities Net Income Excluding Corporate Overhead And Interest Costs ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts	143714000	USD
CY2015	us-gaap	Results Of Operations Production Or Lifting Costs ResultsOfOperationsProductionOrLiftingCosts	167800000	USD
CY2016	us-gaap	Results Of Operations Production Or Lifting Costs ResultsOfOperationsProductionOrLiftingCosts	153914000	USD
CY2017	us-gaap	Results Of Operations Production Or Lifting Costs ResultsOfOperationsProductionOrLiftingCosts	165991000	USD
CY2015	us-gaap	Results Of Operations Revenue From Oil And Gas Producing Activities ResultsOfOperationsRevenueFromOilAndGasProducingActivities	506721000	USD
CY2016	us-gaap	Results Of Operations Revenue From Oil And Gas Producing Activities ResultsOfOperationsRevenueFromOilAndGasProducingActivities	386152000	USD
CY2017	us-gaap	Results Of Operations Revenue From Oil And Gas Producing Activities ResultsOfOperationsRevenueFromOilAndGasProducingActivities	526492000	USD
CY2015	us-gaap	Results Of Operations Sales Or Transfers To Entitys Other Operations ResultsOfOperationsSalesOrTransfersToEntitysOtherOperations	1946000	USD
CY2016	us-gaap	Results Of Operations Sales Or Transfers To Entitys Other Operations ResultsOfOperationsSalesOrTransfersToEntitysOtherOperations	1765000	USD
CY2017	us-gaap	Results Of Operations Sales Or Transfers To Entitys Other Operations ResultsOfOperationsSalesOrTransfersToEntitysOtherOperations	2357000	USD
CY2014Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1614361000	USD
CY2015Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1103200000	USD
CY2016Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	676361000	USD
CY2017Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	851669000	USD
CY2015	us-gaap	Revisions Of Previous Quantity Estimates RevisionsOfPreviousQuantityEstimates	-16573000	USD
CY2016	us-gaap	Revisions Of Previous Quantity Estimates RevisionsOfPreviousQuantityEstimates	6202000	USD
CY2017	us-gaap	Revisions Of Previous Quantity Estimates RevisionsOfPreviousQuantityEstimates	39078000	USD
CY2015	us-gaap	Sales And Transfers Of Oil And Gas Produced Net Of Production Costs SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts	-318753000	USD
CY2016	us-gaap	Sales And Transfers Of Oil And Gas Produced Net Of Production Costs SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts	-218444000	USD
CY2017	us-gaap	Sales And Transfers Of Oil And Gas Produced Net Of Production Costs SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts	-345075000	USD
CY2015	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	1760913000	USD
CY2015Q4	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	375195000	USD
CY2016Q1	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	449132000	USD
CY2016Q2	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	335617000	USD
CY2016Q3	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	292472000	USD
CY2016	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	1452416000	USD
CY2016Q4	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	422500000	USD
CY2017Q1	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	522075000	USD
CY2017Q2	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	348369000	USD
CY2017Q3	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	286937000	USD
CY2017	us-gaap	Sales Revenue Goods Gross SalesRevenueGoodsGross	1579881000	USD
CY2015	us-gaap	Share Based Compensation ShareBasedCompensation	3208000	USD
CY2016	us-gaap	Share Based Compensation ShareBasedCompensation	5755000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	12262000	USD
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	2182243	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	0	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	0.00
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	0	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	0	USD
CY2016Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	19000	shares
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	0	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	0	shares
CY2016Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	39.48
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	0.00
CY2017	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	39.48
CY2017	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	0.00
CY2017	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	0.00
CY2017Q3	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	0	USD
CY2017	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P0Y0M00D
CY2017	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P0Y0M00D
CY2016Q3	us-gaap	Short Term Bank Loans And Notes Payable ShortTermBankLoansAndNotesPayable	0	USD
CY2017Q3	us-gaap	Short Term Bank Loans And Notes Payable ShortTermBankLoansAndNotesPayable	0	USD
CY2016Q3	us-gaap	Short Term Borrowings ShortTermBorrowings	0	USD
CY2017Q3	us-gaap	Short Term Borrowings ShortTermBorrowings	0	USD
CY2015	us-gaap	Standardized Measure Of Discounted Future Net Cash Flow Relating To Proved Oil And Gas Reserves Accretion Of Discount StandardizedMeasureOfDiscountedFutureNetCashFlowRelatingToProvedOilAndGasReservesAccretionOfDiscount	206382000	USD
CY2016	us-gaap	Standardized Measure Of Discounted Future Net Cash Flow Relating To Proved Oil And Gas Reserves Accretion Of Discount StandardizedMeasureOfDiscountedFutureNetCashFlowRelatingToProvedOilAndGasReservesAccretionOfDiscount	22105000	USD
CY2017	us-gaap	Standardized Measure Of Discounted Future Net Cash Flow Relating To Proved Oil And Gas Reserves Accretion Of Discount StandardizedMeasureOfDiscountedFutureNetCashFlowRelatingToProvedOilAndGasReservesAccretionOfDiscount	71080000	USD
CY2014Q3	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	2066878000	USD
CY2015Q3	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	1323034000	USD
CY2016Q3	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	642528000	USD
CY2017Q3	us-gaap	Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves	1113046000	USD
CY2017	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	180247	shares
CY2017	us-gaap	Stock Issued During Period Shares Employee Benefit Plan StockIssuedDuringPeriodSharesEmployeeBenefitPlan	103602	shares
CY2017	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	-19000	shares
CY2017	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	53564	shares
CY2016Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1527004000	USD
CY2017Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1703735000	USD
CY2015	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	89564000	USD
CY2016	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	81714000	USD
CY2017	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	84995000	USD
CY2017	us-gaap	Unrealized Gain Loss On Price Risk Cash Flow Derivatives Before Tax UnrealizedGainLossOnPriceRiskCashFlowDerivativesBeforeTax	35500000	USD
CY2014Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	3147000	USD
CY2015Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	5085000	USD
CY2016Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	396000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	1251000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	566000	USD
CY2016	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	1314000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	396000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2016	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	3771000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2015	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	2504000	USD
CY2016	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	396000	USD
CY2016Q3	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	21109000	USD
CY2017Q3	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	22526000	USD
CY2015	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	9316000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	1251000	USD
CY2016Q3	us-gaap	Unrecovered Costs For Purchased Gas Amount UnrecoveredCostsForPurchasedGasAmount	2440000	USD
CY2017Q3	us-gaap	Unrecovered Costs For Purchased Gas Amount UnrecoveredCostsForPurchasedGasAmount	4623000	USD
CY2016Q3	us-gaap	Unsecured Debt UnsecuredDebt	2099000000	USD
CY2017Q3	us-gaap	Unsecured Debt UnsecuredDebt	2399000000	USD
CY2014Q3	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	31811000	USD
CY2015Q3	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	29029000	USD
CY2016	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	6819000	USD
CY2017	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	6301000	USD
CY2015	us-gaap	Valuation Allowances And Reserves Charged To Other Accounts ValuationAllowancesAndReservesChargedToOtherAccounts	2585000	USD
CY2016	us-gaap	Valuation Allowances And Reserves Charged To Other Accounts ValuationAllowancesAndReservesChargedToOtherAccounts	1521000	USD
CY2017	us-gaap	Valuation Allowances And Reserves Charged To Other Accounts ValuationAllowancesAndReservesChargedToOtherAccounts	1774000	USD
CY2015	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	14683000	USD
CY2016	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	16260000	USD
CY2017	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	6658000	USD
CY2015	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	84387755	shares
CY2016	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	84847993	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	86021386	shares
CY2015	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	84387755	shares
CY2016	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	84847993	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	85364929	shares
CY2017	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-top:10px;text-indent:16px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;">Reclassification</font></div><div style="line-height:120%;padding-top:6px;text-align:justify;text-indent:30px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Certain prior year amounts have been reclassified to conform with current year presentation.</font></div></div>

Files In Submission

Name	View Source	Status
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$NFG
NATIONAL FUEL GAS CO Stock $nfg

2017 Q3 Form 10-K Financial Statement

#000007014517000054 Filed on November 17, 2017

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NFG NATIONAL FUEL GAS CO Stock $nfg

2017 Q3 Form 10-K Financial Statement

#000007014517000054 Filed on November 17, 2017

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NFG
NATIONAL FUEL GAS CO Stock $nfg