$ES
EVERSOURCE ENERGY Stock $es

$es Overview Financials Valuation SEC Filings Company Website

2014 Q4 Form 10-K Financial Statement

#000007274116000063 Filed on February 26, 2016

Income Statement

Concept	2014 Q4	2014 Q3	2014 Q2
Revenue	$1.881B	$1.893B	$1.678B
YoY Change	5.82%	-0.01%	2.55%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$158.5M	$153.2M	$152.2M
YoY Change	7.68%	2.75%	-4.6%
% of Gross Profit
Operating Expenses	$1.451B	$1.452B	$1.384B
YoY Change	2.39%	-2.79%	7.65%
Operating Profit	$430.2M	$440.9M	$294.0M
YoY Change	19.3%	10.42%	-16.14%
Interest Expense	-$89.90M	$89.74M	$92.50M
YoY Change	2.04%	2.59%	6.5%
% of Operating Profit	-20.9%	20.35%	31.46%
Other Income/Expense, Net	$5.600M	$11.86M	$5.526M
YoY Change	-31.71%	32.59%	11.77%
Pretax Income	$345.9M	$363.0M	$207.0M
YoY Change	23.18%	13.2%	-22.95%
Income Tax	$122.4M	$126.5M	$77.77M
% Of Pretax Income	35.39%	34.86%	37.57%
Net Earnings	$223.6M	$236.5M	$129.2M
YoY Change	24.78%	11.87%	-25.36%
Net Earnings / Revenue	11.89%	12.5%	7.7%
Basic Earnings Per Share		$0.74	$0.40
Diluted Earnings Per Share	$696.6K	$0.74	$0.40
COMMON SHARES
Basic Shares Outstanding	316.8M shares	316.3M shares	316.0M shares
Diluted Shares Outstanding		317.6M shares	317.1M shares

Balance Sheet

Concept	2014 Q4	2014 Q3	2014 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$39.00M	$156.0M	$150.0M
YoY Change	-9.3%	168.97%	316.67%
Cash & Equivalents	$39.00M	$42.00M	$34.00M
Short-Term Investments		$115.0M	$116.0M
Other Short-Term Assets	$1.110B	$762.0M	$829.0M
YoY Change	417.99%	-12.51%	375.12%
Inventory	$350.0M	$334.0M	$282.0M
Prepaid Expenses
Receivables	$856.0M	$849.0M	$808.0M
Other Receivables	$338.0M	$0.00	$0.00
Total Short-Term Assets	$2.692B	$2.102B	$2.068B
YoY Change	28.99%	4.16%	0.82%
LONG-TERM ASSETS
Property, Plant & Equipment	$18.65B	$18.25B	$17.98B
YoY Change	6.09%	6.2%	6.18%
Goodwill	$3.519B
YoY Change	0.0%
Intangibles
YoY Change
Long-Term Investments	$515.0M	$518.0M	$514.0M
YoY Change	5.32%	10.68%	2.39%
Other Assets	$312.4M	$3.589B	$3.710B
YoY Change	7.15%	-31.65%	1195.12%
Total Long-Term Assets	$8.401B	$25.88B	$25.72B
YoY Change	3.3%	-2.07%	179.15%
TOTAL ASSETS
Total Short-Term Assets	$2.692B	$2.102B	$2.068B
Total Long-Term Assets	$8.401B	$25.88B	$25.72B
Total Assets	$29.74B	$27.98B	$27.79B
YoY Change	7.0%	-1.62%	-1.44%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$868.2M	$609.0M	$562.0M
YoY Change	16.97%	9.93%	5.64%
Accrued Expenses
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$957.0M	$1.047B	$905.0M
YoY Change	-12.44%	-22.04%	13.84%
Long-Term Debt Due	$245.6M	$246.0M	$396.0M
YoY Change	-53.95%	-59.54%	-55.41%
Total Short-Term Liabilities	$3.134B	$2.930B	$2.803B
YoY Change	-4.31%	-13.26%	-9.05%
LONG-TERM LIABILITIES
Long-Term Debt	$8.606B	$8.167B	$8.147B
YoY Change	10.66%	9.71%	6.48%
Other Long-Term Liabilities	$874.4M	$2.582B	$2.661B
YoY Change	-5.27%	-35.35%	195.91%
Total Long-Term Liabilities	$7.905B	$10.75B	$10.81B
YoY Change	13.32%	-6.02%	36.78%
TOTAL LIABILITIES
Total Short-Term Liabilities	$3.134B	$2.930B	$2.803B
Total Long-Term Liabilities	$7.905B	$10.75B	$10.81B
Total Liabilities	$11.04B	$17.94B	$17.88B
YoY Change	7.69%	-4.45%	-4.05%
SHAREHOLDERS EQUITY
Retained Earnings	$2.449B
YoY Change	15.18%
Common Stock	$1.667B
YoY Change	0.09%
Preferred Stock
YoY Change
Treasury Stock (at cost)	-$300.5M
YoY Change	-7.98%
Treasury Stock Shares	16.38M shares	16.73M shares	17.11M shares
Shareholders Equity	$9.977B	$10.05B	$9.909B
YoY Change
Total Liabilities & Shareholders Equity	$29.78B	$27.98B	$27.79B
YoY Change	7.13%	-1.62%	-1.44%

Cashflow Statement

Concept	2014 Q4	2014 Q3	2014 Q2
OPERATING ACTIVITIES
Net Income	$223.6M	$236.5M	$129.2M
YoY Change	24.78%	11.87%	-25.36%
Depreciation, Depletion And Amortization	$158.5M	$153.2M	$152.2M
YoY Change	7.68%	2.75%	-4.6%
Cash From Operating Activities	$248.0M	$507.3M	$402.9M
YoY Change	-49.02%	24.34%	36.16%
INVESTING ACTIVITIES
Capital Expenditures	-$486.2M	-$393.5M	-$375.3M
YoY Change	26.95%	5.35%	20.56%
Acquisitions
YoY Change
Other Investing Activities	$17.60M	-$8.300M	$5.100M
YoY Change	2100.0%	-125.62%	-87.38%
Cash From Investing Activities	-$468.6M	-$401.8M	-$370.2M
YoY Change	22.61%	17.76%	36.66%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	217.7M	-98.00M	-87.60M
YoY Change	-283.1%	118.26%	76.26%
NET CHANGE
Cash From Operating Activities	248.0M	507.3M	402.9M
Cash From Investing Activities	-468.6M	-401.8M	-370.2M
Cash From Financing Activities	217.7M	-98.00M	-87.60M
Net Change In Cash	-2.900M	7.500M	-54.90M
YoY Change	-80.14%	-65.75%	122.27%
FREE CASH FLOW
Cash From Operating Activities	$248.0M	$507.3M	$402.9M
Capital Expenditures	-$486.2M	-$393.5M	-$375.3M
Free Cash Flow	$734.2M	$900.8M	$778.2M
YoY Change	-15.56%	15.27%	28.16%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2015Q4	us-gaap	Assets Noncurrent AssetsNoncurrent	8069082000	USD
CY2015Q4	us-gaap	Assets Assets	30580309000	USD
CY2014Q4	us-gaap	Goodwill Goodwill	3519401000	USD
CY2014Q4	us-gaap	Assets Noncurrent AssetsNoncurrent	8400881000	USD
CY2014Q4	us-gaap	Deferred Tax Liabilities Current DeferredTaxLiabilitiesCurrent	160288000	USD
CY2015Q4	us-gaap	Notes Payable NotesPayable	1160953000	USD
CY2013	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	1220630000	USD
CY2013	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	426941000	USD
CY2015	us-gaap	Net Income Loss NetIncomeLoss	886004000	USD
CY2014	us-gaap	Interest Expense InterestExpense	362106000	USD
CY2015	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	539967000	USD
CY2015	us-gaap	Interest Expense InterestExpense	372420000	USD
CY2013	us-gaap	Interest Expense InterestExpense	338699000	USD
CY2013	us-gaap	Net Income Loss NetIncomeLoss	793689000	USD
CY2015	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	7519000	USD
CY2014Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	668432000	USD
CY2015Q4	us-gaap	Liabilities Current LiabilitiesCurrent	2989790000	USD
CY2014Q4	us-gaap	Liabilities Current LiabilitiesCurrent	3134381000	USD
CY2015Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	107759000	USD
CY2014Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	235022000	USD
CY2015Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	678549000	USD
CY2013	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	7682000	USD
CY2015	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	878485000	USD
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	19892441000	USD
CY2015Q4	us-gaap	Goodwill Goodwill	3519401000	USD
CY2015Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	845843000	USD
CY2014Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	672493000	USD
CY2015	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	1329289000	USD
CY2014	us-gaap	Net Income Loss NetIncomeLoss	827065000	USD
CY2015	us-gaap	Increase Decrease In Regulatory Assets And Liabilities IncreaseDecreaseInRegulatoryAssetsAndLiabilities	163287000	USD
CY2015	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-91945000	USD
CY2014Q4	us-gaap	Redeemable Noncontrolling Interest Equity Preferred Carrying Amount RedeemableNoncontrollingInterestEquityPreferredCarryingAmount	155568000	USD
CY2015Q4	us-gaap	Redeemable Noncontrolling Interest Equity Preferred Carrying Amount RedeemableNoncontrollingInterestEquityPreferredCarryingAmount	155568000	USD
CY2014	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	819546000	USD
CY2013	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	786007000	USD
CY2015	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	1425971000	USD
CY2014	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	1295362000	USD
CY2014	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	468297000	USD
CY2014	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	1427589000	USD
CY2013	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	1514986000	USD
CY2013	es	Energy Efficiency Programs EnergyEfficiencyPrograms	401919000	USD
CY2015	es	Energy Efficiency Programs EnergyEfficiencyPrograms	495701000	USD
CY2014	es	Energy Efficiency Programs EnergyEfficiencyPrograms	473127000	USD
CY2015	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	34227000	USD
CY2014	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	24619000	USD
CY2013	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	29894000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	2079000	USD
CY2014	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	2037000	USD
CY2013	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	2049000	USD
CY2013	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-940000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-2588000	USD
CY2014	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	315000	USD
CY2014	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-30330000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	7674000	USD
CY2013	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	25714000	USD
CY2013	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	26823000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	7165000	USD
CY2014	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-27978000	USD
CY2014	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	7519000	USD
CY2015	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	7519000	USD
CY2013	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	7682000	USD
CY2013	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	812830000	USD
CY2015	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	885650000	USD
CY2014	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	791568000	USD
CY2014	es	Sharesissuedvalueinconectionwithnstarmerger Sharesissuedvalueinconectionwithnstarmerger		USD
CY2014	es	Sharesissuedinconnectionwithnstarmerger Sharesissuedinconnectionwithnstarmerger		shares
CY2015	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	491736000	USD
CY2015	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	96017000	USD
CY2014	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	7519000	USD
CY2015	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	39797000	USD
CY2012Q4	us-gaap	Cash Cash	45748000	USD
CY2015	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	529791000	USD
CY2015	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	7519000	USD
CY2015	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-34112000	USD
CY2015	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	-30282000	USD
CY2015	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	-91618000	USD
CY2015	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-44031000	USD
CY2015	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1424025000	USD
CY2015	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1724139000	USD
CY2015	us-gaap	Proceeds From Sale And Maturity Of Marketable Securities ProceedsFromSaleAndMaturityOfMarketableSecurities	799165000	USD
CY2015	us-gaap	Payments To Acquire Marketable Securities PaymentsToAcquireMarketableSecurities	717114000	USD
CY2015	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	17062000	USD
CY2015	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1659150000	USD
CY2015	us-gaap	Repayments Of Secured Debt RepaymentsOfSecuredDebt	0	USD
CY2015	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-8499000	USD
CY2015	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	220369000	USD
CY2015	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-14756000	USD
CY2015	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	216700000	USD
CY2013	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	431413000	USD
CY2013	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	195698000	USD
CY2013	us-gaap	Increase Decrease In Regulatory Assets And Liabilities IncreaseDecreaseInRegulatoryAssetsAndLiabilities	24276000	USD
CY2013	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	56071000	USD
CY2013	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	163549000	USD
CY2013	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	14811000	USD
CY2013	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	50950000	USD
CY2013	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	-54619000	USD
CY2013	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	22623000	USD
CY2013	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1663539000	USD
CY2013	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1456787000	USD
CY2013	us-gaap	Proceeds From Sale And Maturity Of Marketable Securities ProceedsFromSaleAndMaturityOfMarketableSecurities	627532000	USD
CY2013	us-gaap	Payments To Acquire Marketable Securities PaymentsToAcquireMarketableSecurities	679784000	USD
CY2013	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-67816000	USD
CY2013	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1441223000	USD
CY2013	us-gaap	Repayments Of Secured Debt RepaymentsOfSecuredDebt	82139000	USD
CY2013	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	929885000	USD
CY2015	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-242122000	USD
CY2015	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	1225000000	USD
CY2013	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	462741000	USD
CY2013	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	7682000	USD
CY2013	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-397000000	USD
CY2013	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	1680000000	USD
CY2015	us-gaap	Pension And Other Postretirement Benefit Contributions PensionAndOtherPostretirementBenefitContributions	162452000	USD
CY2013	us-gaap	Pension And Other Postretirement Benefit Contributions PensionAndOtherPostretirementBenefitContributions	342184000	USD
CY2014	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	443259000	USD
CY2014	us-gaap	Pension And Other Postretirement Benefit Contributions PensionAndOtherPostretirementBenefitContributions	211649000	USD
CY2014	us-gaap	Increase Decrease In Regulatory Assets And Liabilities IncreaseDecreaseInRegulatoryAssetsAndLiabilities	-6853000	USD
CY2014	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	122139000	USD
CY2014	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	41310000	USD
CY2014	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	323224000	USD
CY2014	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	144743000	USD
CY2014	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-15797000	USD
CY2014	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1635473000	USD
CY2014	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1603744000	USD
CY2014	us-gaap	Proceeds From Sale And Maturity Of Marketable Securities ProceedsFromSaleAndMaturityOfMarketableSecurities	488789000	USD
CY2014	us-gaap	Payments To Acquire Marketable Securities PaymentsToAcquireMarketableSecurities	491220000	USD
CY2014	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-14380000	USD
CY2014	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1591795000	USD
CY2014	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	475227000	USD
CY2014	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	7519000	USD
CY2014	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	285075000	USD
CY2014	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	725000000	USD
CY2014	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	576551000	USD
CY2014	us-gaap	Repayments Of Secured Debt RepaymentsOfSecuredDebt	0	USD
CY2014	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	883000	USD
CY2014	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-48339000	USD
CY2014	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-4661000	USD
CY2013Q4	us-gaap	Cash Cash	43364000	USD
CY2015Q4	es	Payment Refund Relatedto Spent Nuclear Fuel PaymentRefundRelatedtoSpentNuclearFuel	-297253000	USD
CY2014Q4	es	Payment Refund Relatedto Spent Nuclear Fuel PaymentRefundRelatedtoSpentNuclearFuel	132138000	USD
CY2015Q4	es	Available For Sale Securities Subject To New Accounting Guidance AvailableForSaleSecuritiesSubjectToNewAccountingGuidance	52000000	USD
CY2014Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	175300000	USD
CY2015Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	190700000	USD
CY2015Q4	es	Uncollectible Hardship Accounts Receivable Reserve UncollectibleHardshipAccountsReceivableReserve	118500000	USD
CY2014Q4	es	Uncollectible Hardship Accounts Receivable Reserve UncollectibleHardshipAccountsReceivableReserve	91500000	USD
CY2015Q4	es	Cash Collateral Deposited CashCollateralDeposited	17100000	USD
CY2014Q4	es	Cash Collateral Deposited CashCollateralDeposited	9900000	USD
CY2015	es	Fuel Power Costs FuelPowerCosts	516700000	USD
CY2014	es	Fuel Power Costs FuelPowerCosts	599400000	USD
CY2013	es	Fuel Power Costs FuelPowerCosts	466500000	USD
CY2015	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	-7200000	USD
CY2015	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	18800000	USD
CY2015	es	Public Utilities Allowance For Funds Used During Construction Capitalized Total PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedTotal	26000000	USD
CY2014	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	-5800000	USD
CY2014	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	13700000	USD
CY2014	es	Public Utilities Allowance For Funds Used During Construction Capitalized Total PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedTotal	19500000	USD
CY2013	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	-4100000	USD
CY2013	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	7100000	USD
CY2013	es	Public Utilities Allowance For Funds Used During Construction Capitalized Total PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedTotal	11200000	USD
CY2015	us-gaap	Public Utilities Allowance For Funds Used During Construction Rate PublicUtilitiesAllowanceForFundsUsedDuringConstructionRate	0.039	pure
CY2014	us-gaap	Public Utilities Allowance For Funds Used During Construction Rate PublicUtilitiesAllowanceForFundsUsedDuringConstructionRate	0.034	pure
CY2013	us-gaap	Public Utilities Allowance For Funds Used During Construction Rate PublicUtilitiesAllowanceForFundsUsedDuringConstructionRate	0.027	pure
CY2015	us-gaap	Excise And Sales Taxes ExciseAndSalesTaxes	147200000	USD
CY2014	us-gaap	Excise And Sales Taxes ExciseAndSalesTaxes	148200000	USD
CY2013	us-gaap	Excise And Sales Taxes ExciseAndSalesTaxes	144100000	USD
CY2015	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	6600000	USD
CY2015	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	216600000	USD
CY2014	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	181900000	USD
CY2013	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	193100000	USD
CY2015	us-gaap	Interest Paid Net InterestPaidNet	365900000	USD
CY2014	us-gaap	Interest Paid Net InterestPaidNet	349600000	USD
CY2013	us-gaap	Interest Paid Net InterestPaidNet	343300000	USD
CY2013	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	50000000	USD
CY2014	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	334200000	USD
CY2015	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	10300000	USD
CY2015	us-gaap	Description Of Postemployment Benefits DescriptionOfPostemploymentBenefits	For the years ended December 31, 2015, 2014 and 2013, Eversource recorded severance benefit expense of $4.7 million, $15 million and $9.7 million, respectively, in connection with organizational and cost saving initiatives, and, in 2014, the partial outsourcing of information technology functions. As of December 31, 2015 and 2014, the severance accrual totaled $9.3 million and $10.4 million, respectively, and was included in Other Current Liabilities on the balance sheets.
CY2014	us-gaap	Postemployment Benefits Period Expense PostemploymentBenefitsPeriodExpense	15000000	USD
CY2014Q4	us-gaap	Postemployment Benefits Liability Current PostemploymentBenefitsLiabilityCurrent	10400000	USD
CY2015	us-gaap	Postemployment Benefits Period Expense PostemploymentBenefitsPeriodExpense	4700000	USD
CY2015Q4	us-gaap	Postemployment Benefits Liability Current PostemploymentBenefitsLiabilityCurrent	9300000	USD
CY2013	us-gaap	Postemployment Benefits Period Expense PostemploymentBenefitsPeriodExpense	9700000	USD
CY2015Q4	us-gaap	Regulatory Assets RegulatoryAssets	4583800000	USD
CY2014Q4	us-gaap	Regulatory Assets RegulatoryAssets	4726600000	USD
CY2015Q4	us-gaap	Amount Of Regulatory Costs Not Yet Approved AmountOfRegulatoryCostsNotYetApproved	75300000	USD
CY2014Q4	us-gaap	Amount Of Regulatory Costs Not Yet Approved AmountOfRegulatoryCostsNotYetApproved	60500000	USD
CY2015	us-gaap	Description Of Regulatory Assets And Liabilities DescriptionOfRegulatoryAssetsAndLiabilities	Benefit Costs: Eversource's Pension, SERP and PBOP Plans are accounted for in accordance with accounting guidance on defined benefit pension and other PBOP plans. The liability recorded by the Regulated companies to recognize the funded status of their retiree benefit plans is offset by a regulatory asset in lieu of a charge to Accumulated Other Comprehensive Income/(Loss), reflecting ultimate recovery from customers through rates. The regulatory asset is amortized as the actuarial gains and losses and prior service cost are amortized to net periodic benefit cost for the pension and PBOP plans.  All amounts are remeasured annually. Regulatory accounting is also applied to the portions of Eversource's service company costs that support the Regulated companies, as these amounts are also recoverable. As these regulatory assets do not represent a cash outlay for the Regulated companies, no carrying charge is recovered from customers. CL&P, NSTAR Electric, PSNH and WMECO recover benefit costs related to their distribution and transmission operations from customers in rates as allowed by their applicable regulatory commissions. NSTAR Electric and WMECO each recover their qualified pension and PBOP expenses related to distribution operations through rate reconciling mechanisms that fully track the change in net pension and PBOP expenses each year. Derivative Liabilities: Regulatory assets are recorded as an offset to derivative liabilities and relate to the fair value of contracts used to purchase energy and energy-related products that will be recovered from customers in future rates. These assets are excluded from rate base and are being recovered as the actual settlements occur over the duration of the contracts. See Note 4, "Derivative Instruments," to the financial statements for further information on these contracts. Income Taxes, Net: The tax effect of temporary book-tax differences (differences between the periods in which transactions affect income in the financial statements and the periods in which they affect the determination of taxable income, including those differences relating to uncertain tax positions) is accounted for in accordance with the rate-making treatment of the applicable regulatory commissions and accounting guidance for income taxes. Differences in income taxes between the accounting guidance and the rate-making treatment of the applicable regulatory commissions are recorded as regulatory assets. As these assets are offset by deferred income tax liabilities, no carrying charge is collected. The amortization period of these assets varies depending on the nature and/or remaining life of the underlying assets and liabilities.  For further information regarding income taxes, see Note 10, "Income Taxes," to the financial statements. Storm Restoration Costs: The storm restoration cost deferrals relate to costs incurred for major storm events at CL&P, NSTAR Electric, PSNH and WMECO that each company expects to recover from customers. A storm must meet certain criteria to qualify as a major storm with the criteria specific to each state jurisdiction and utility company. Once a storm qualifies as a major storm, all qualifying expenses incurred during storm restoration efforts are deferred and recovered from customers. In addition to storm restoration costs, CL&P and PSNH are each allowed to recover pre-staging storm costs. Of the total deferred storm restoration costs, $197 million is pending regulatory approval (including $106 million at NSTAR Electric, $61 million at PSNH, and $30 million at WMECO). Management believes the storm restoration costs were prudent and meet the criteria for specific cost recovery in Connecticut, Massachusetts and New Hampshire, and that recovery from customers is probable through the applicable regulatory recovery process. Each electric utility has sought, or is seeking, recovery of its deferred storm restoration costs through its applicable regulatory recovery process. Each electric utility company earns a return on its deferred storm restoration cost regulatory asset balance. Goodwill-related: The goodwill regulatory asset originated from a 1999 merger transaction and the DPU allowed its recovery in NSTAR Electric and NSTAR Gas rates. This regulatory asset is currently being amortized and recovered from customers in rates without a carrying charge over a 40-year period, and, as of December 31, 2015, there were 24 years of amortization remaining. Regulatory Tracker Mechanisms: The Regulated companies’ approved rates are designed to recover their costs incurred to provide service to customers. The Regulated companies recover certain of their costs on a fully-reconciling basis through regulatory commission-approved tracking mechanisms. The differences between the costs incurred (or the rate recovery allowed) and the actual revenues are recorded as regulatory assets (for undercollections) or as regulatory liabilities (for overcollections) to be included in future customer rates each year. Carrying charges are recorded on all material regulatory tracker mechanisms. CL&P, NSTAR Electric, PSNH and WMECO each recover, on a fully reconciling basis, the costs associated with the procurement of energy, transmission related costs from FERC-approved transmission tariffs, energy efficiency programs (including LBR at NSTAR Electric), low income assistance programs, certain uncollectible accounts receivable for hardship customers, and restructuring and stranded costs as a result of deregulation. Energy procurement costs at PSNH include the costs related to its generating stations and at WMECO include the costs related to its solar generation. CL&P (effective December 1, 2014) and WMECO each have a regulatory commission approved revenue decoupling mechanism. Distribution revenues are decoupled from customer sales volumes, which breaks the relationship between sales volumes and revenues recognized. CL&P and WMECO reconcile their annual base distribution rate recovery to pre-established levels of baseline distribution delivery service revenues. Any difference between the allowed level of distribution revenue and the actual amount received during a 12-month period is adjusted through rates in the following period. CL&P and WMECO's revenue decoupling mechanisms permit recovery of an annual base amount of distribution revenues of $1.059 billion and $132.4 million, respectively. Contractual Obligations - Yankee Companies: CL&P, NSTAR Electric, PSNH and WMECO are responsible for their proportionate share of the remaining costs of the CYAPC, YAEC and MYAPC nuclear facilities, including nuclear fuel storage. A portion of these costs was recorded as a regulatory asset. Amounts for CL&P are earning a return and are being recovered through the CTA. Amounts for NSTAR Electric and WMECO are being recovered without a return through the transition charge. Amounts for PSNH were fully recovered in 2006. As a result of Eversource's consolidation of CYAPC and YAEC, Eversource's regulatory asset balance also includes the regulatory assets of CYAPC and YAEC, which totaled $110.9 million and $97.8 million as of December 31, 2015 and 2014, respectively. Intercompany transactions between CL&P, NSTAR Electric, PSNH and WMECO and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Other Regulatory Assets: Other Regulatory Assets primarily include asset retirement obligations, environmental remediation costs, losses associated with the reacquisition or redemption of long-term debt, purchase power contract termination costs and various other items. Regulatory Costs in Other Long-Term Assets: The Regulated companies had $75.3 million (including $3.1 million for CL&P, $35.4 million for NSTAR Electric, $4.8 million for PSNH and $16.7 million for WMECO) and $60.5 million (including $1.3 million for CL&P, $33.2 million for NSTAR Electric, $0.9 million for PSNH, and $11 million for WMECO) of additional regulatory costs as of December 31, 2015 and 2014, respectively, that were included in Other Long-Term Assets on the balance sheets. These amounts represent incurred costs for which recovery has not yet been specifically approved by the applicable regulatory agency. However, based on regulatory policies or past precedent on similar costs, management believes it is probable that these costs will ultimately be approved and recovered from customers in rates. The NSTAR Electric balance as of December 31, 2015 and 2014 primarily related to the deferral of certain bad debt costs expected to be recovered in future rates. Equity Return on Regulatory Assets: For rate-making purposes, the Regulated companies recover the carrying costs related to their regulatory assets. For certain regulatory assets, the carrying cost recovered includes an equity return component. This equity return, which is not recorded on the balance sheets, totaled $1.5 million and $1.7 million for CL&P as of December 31, 2015 and 2014, respectively. These carrying costs will be recovered from customers in future rates. As of December 31, 2015 and 2014, this equity return, which is not recorded on the balance sheets, totaled $48.3 million and $43.3 million, respectively, for PSNH. These amounts include $25 million of equity return on the Clean Air Project costs that PSNH has agreed not to bill customers pending NHPUC approval of a generation divestiture settlement agreement. For further information on the divestiture, see Note 11H, "Commitments and Contingencies – PSNH Generation Restructuring." Regulatory Liabilities: The components of regulatory liabilities were as follows: Cost of Removal: Eversource's Regulated companies currently recover amounts in rates for future costs of removal of plant assets over the lives of the assets. The estimated cost to remove utility assets from service is recognized as a component of depreciation expense and the cumulative amount collected from customers but not yet expended is recognized as a regulatory liability. Expended costs that exceed amounts collected from customers are recognized as regulatory assets, as they are probable of recovery in future rates. AFUDC - Transmission: Regulatory liabilities were recorded by CL&P and WMECO for AFUDC accrued on certain reliability-related transmission projects to reflect local rate base recovery as a result of a FERC-approved transmission tariff. A regulatory liability was recorded by NSTAR Electric for AFUDC accrued on certain reliability-related transmission projects through December 31, 2015 to reflect local rate base recovery. These regulatory liabilities for CL&P, NSTAR Electric and WMECO will be amortized over the depreciable life of the related transmission assets.
CY2015Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	621400000	USD
CY2014Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	750100000	USD
CY2015	us-gaap	Public Utilities Disclosure Of Regulatory Matters Pending PublicUtilitiesDisclosureOfRegulatoryMattersPending	2015 Regulatory Developments: FERC ROE Complaints: As a result of the actions taken by the FERC and other developments in the pending ROE complaint proceedings described in Note 11E, "Commitments and Contingencies – FERC ROE Complaints," Eversource recorded reserves for the first and second ROE complaints, which were recorded as a regulatory liability and as a reduction to operating revenues. The cumulative pre-tax reserves (excluding interest) as of December 31, 2015, which include the impact of refunds given to customers, totaled $39.1 million for Eversource (including $21.4 million for CL&P, $8.5 million for NSTAR Electric, $3.1 million for PSNH, and $6.1 million for WMECO). NSTAR Electric and NSTAR Gas Comprehensive Settlement Agreement: On March 2, 2015, the DPU approved the comprehensive settlement agreement between NSTAR Electric, NSTAR Gas and the Massachusetts Attorney General (the "Settlement") as filed with the DPU on December 31, 2014. The Settlement resolved the outstanding NSTAR Electric CPSL program filings for 2006 through 2011, the NSTAR Electric and NSTAR Gas PAM and energy efficiency-related customer billing adjustments reported in 2012, and the recovery of LBR related to NSTAR Electric's energy efficiency programs for 2009 through 2011 (11 dockets in total). In 2015, as a result of the DPU order, NSTAR Electric and NSTAR Gas commenced refunding a combined $44.7 million to customers, which was recorded as a regulatory liability. Refunds to customers will continue through December 2016. As a result of the Settlement, NSTAR Electric increased its operating revenues and decreased its amortization expense in 2015, resulting in the recognition of a $21.7 million pre-tax benefit in 2015. NSTAR Electric Basic Service Bad Debt Adder: On January 7, 2015, the DPU issued an order concluding that NSTAR Electric had removed energy-related bad debt costs from base distribution rates effective January 1, 2006. As a result of the DPU order, in the first quarter of 2015, NSTAR Electric increased its regulatory assets and reduced its operations and maintenance expense by an under recovered amount of $24.2 million for energy-related bad debt costs through 2014, resulting in a pre-tax benefit in 2015. NSTAR Electric filed for recovery of the energy-related bad debt costs regulatory asset from customers and on November 20, 2015 the DPU approved NSTAR Electric’s proposed rate increase to recover these costs over a 12-month period, effective January 1, 2016. CL&P Distribution Rates: On July 2, 2015, PURA issued a final order that approved a settlement agreement filed on May 19, 2015, which allows for an increase to rate base of approximately $163 million associated with ADIT, including a regulatory asset to recover the incremental revenue requirement for the period December 1, 2014 through November 30, 2015 over a subsequent 24-month period. The rate base increase provided an increase to total allowed annual revenue requirements of $18.4 million beginning December 1, 2014. As part of the settlement agreement, the $18.4 million for the period December 1, 2014 through November 30, 2015 was recorded as a regulatory asset with a corresponding increase in Operating Revenues, and is being collected from customers in rates over a 24-month period beginning December 1, 2015. NSTAR Gas Distribution Rates: On October 30, 2015, the DPU issued its order in the NSTAR Gas distribution rate case, which approved an annualized base rate increase of $15.8 million, plus other increases of approximately $11.5 million, mostly relating to recovery of pension and PBOP expenses and the Hopkinton GSA, effective January 1, 2016. In the order, the DPU also approved an authorized regulatory ROE of 9.8 percent, the establishment of a revenue decoupling mechanism, the recovery of certain bad debt expenses, and a 52.1 percent equity component of its capital structure. On November 19, 2015, NSTAR Gas filed a motion for reconsideration of the order with the DPU seeking the correction of mathematical errors and other plant and cost of service items. As a result of this order, Eversource recorded regulatory deferrals for costs that have been approved for recovery or are expected to be approved for recovery in future rate proceedings, which resulted in the recognition of a $17.2 million pre-tax benefit in 2015. Included in this amount is a $10.5 million pre-tax benefit recorded at NSTAR Electric for certain uncollectible hardship accounts receivable that are expected to be recovered in future rates given the allowed recoveries of uncollectible hardship accounts receivable by WMECO and NSTAR Gas.
CY2015	us-gaap	Property Plant And Equipment Depreciation Methods PropertyPlantAndEquipmentDepreciationMethods	Utility property, plant and equipment is recorded at original cost. Original cost includes materials, labor, construction overhead and AFUDC for regulated property. The cost of repairs and maintenance, including planned major maintenance activities, is charged to Operating Expenses as incurred. As of December 31, 2015, PSNH had $1.2 billion in gross generation utility plant assets and related Accumulated Depreciation of $522.4 million. These generation assets are the subject of a divestiture agreement entered into on June 10, 2015 between Eversource, PSNH and key New Hampshire officials whereby, among other resolutions, PSNH has agreed to divest these generation assets upon NHPUC approval. Upon completion of the divestiture process, remaining costs not recovered by the sale of these assets (stranded costs) will be recovered via bonds that will be secured by a non-bypassable charge or other recovery mechanisms in rates billed to PSNH’s customers. See Note 11H, “Commitments and Contingencies – PSNH Generation Restructuring,” for further information. Depreciation of utility assets is calculated on a straight-line basis using composite rates based on the estimated remaining useful lives of the various classes of property (estimated useful life for PSNH distribution). The composite rates, which are subject to approval by the appropriate state regulatory agency, include a cost of removal component (other than PSNH Generation), which is collected from customers over the lives of the plant assets and is recognized as a regulatory liability. Depreciation rates are applied to property from the time it is placed in service. Upon retirement from service, the cost of the utility asset is charged to the accumulated provision for depreciation. The actual incurred removal costs are applied against the related regulatory liability.
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	13054800000	USD
CY2015Q4	es	Public Utilities Property Plant And Equipment Distribution Natural Gas PublicUtilitiesPropertyPlantAndEquipmentDistributionNaturalGas	2727200000	USD
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	7691900000	USD
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Generation Or Processing PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing	1194100000	USD
CY2015Q4	es	Public Utilities Property Plant And Equipment Electric And Natural Gas Utility Total PublicUtilitiesPropertyPlantAndEquipmentElectricAndNaturalGasUtilityTotal	24668000000	USD
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	558600000	USD
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	25226600000	USD
CY2015Q4	es	Electric And Natural Gas Utility Accumulated Depreciation ElectricAndNaturalGasUtilityAccumulatedDepreciation	6141100000	USD
CY2015Q4	es	Other Accumulated Depreciation OtherAccumulatedDepreciation	255600000	USD
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	6396700000	USD
CY2015Q4	es	Property Plant And Equipment Net Excluding Construction Work In Progress PropertyPlantAndEquipmentNetExcludingConstructionWorkInProgress	18829900000	USD
CY2015Q4	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	1062500000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	12495200000	USD
CY2014Q4	es	Public Utilities Property Plant And Equipment Distribution Natural Gas PublicUtilitiesPropertyPlantAndEquipmentDistributionNaturalGas	2595400000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	6930700000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Generation Or Processing PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing	1170900000	USD
CY2014Q4	es	Public Utilities Property Plant And Equipment Electric And Natural Gas Utility Total PublicUtilitiesPropertyPlantAndEquipmentElectricAndNaturalGasUtilityTotal	23192200000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	551300000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	23743500000	USD
CY2014Q4	es	Electric And Natural Gas Utility Accumulated Depreciation ElectricAndNaturalGasUtilityAccumulatedDepreciation	5777800000	USD
CY2014Q4	es	Other Accumulated Depreciation OtherAccumulatedDepreciation	231800000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	6009600000	USD
CY2014Q4	es	Property Plant And Equipment Net Excluding Construction Work In Progress PropertyPlantAndEquipmentNetExcludingConstructionWorkInProgress	17733900000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	913100000	USD
CY2015	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.029	pure
CY2014	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.030	pure
CY2013	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.028	pure
CY2015Q4	es	Distribution Assets Average Useful Life DistributionAssetsAverageUsefulLife	34.8	pure
CY2015Q4	es	Transmission Assets Average Useful Life TransmissionAssetsAverageUsefulLife	41.6	pure
CY2015Q4	es	Generation Assets Average Useful Life GenerationAssetsAverageUsefulLife	30.7	pure
CY2015Q4	es	Other Assets Average Useful Life OtherAssetsAverageUsefulLife	14.1	pure
CY2015	us-gaap	Description Of Derivative Activity Volume DescriptionOfDerivativeActivityVolume	Commodity Supply and Price Risk Management: As required by regulation, CL&P, along with UI, has capacity-related contracts with generation facilities. CL&P has a sharing agreement with UI, with 80 percent of the costs or benefits of each contract borne by or allocated to CL&P and 20 percent borne by or allocated to UI. The combined capacity of these contracts is 787 MW. The capacity contracts extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set capacity price and the capacity market price received in the ISO-NE capacity markets. In addition, CL&P has a contract to purchase 0.1 million MWh of energy per year through 2020. NSTAR Electric has a renewable energy contract to purchase 0.1 million MWh of energy per year through 2018 and a capacity-related contract to purchase up to 35 MW per year through 2019. As of December 31, 2015 and 2014, Eversource had NYMEX financial contracts for natural gas futures in order to reduce variability associated with the purchase price of approximately 9.1 million and 8.8 million MMBtu of natural gas, respectively.
CY2015Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	5800000	USD
CY2014Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	10000000	USD
CY2015Q4	us-gaap	Additional Collateral Aggregate Fair Value AdditionalCollateralAggregateFairValue	5800000	USD
CY2014Q4	us-gaap	Additional Collateral Aggregate Fair Value AdditionalCollateralAggregateFairValue	10000000	USD
CY2015	es	Fairvalueinputsexitpricepremium Fairvalueinputsexitpricepremium	Exit price premiums of 5 percent to 22 percent are also applied on these contracts and reflect the uncertainty and illiquidity premiums that would be required based on the most recent market activity available for similar type contracts
CY2013Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	635200000	USD
CY2014	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements	78500000	USD
CY2014Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	415400000	USD
CY2015Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	380900000	USD
CY2015	es	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilityGainLossIncludedInRegAssetLiability	-52100000	USD
CY2015	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements	86600000	USD
CY2014	es	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilityGainLossIncludedInRegAssetLiability	141300000	USD
CY2014Q4	es	Fair Value Of Securities Under Fair Value Option FairValueOfSecuritiesUnderFairValueOption	85100000	USD
CY2015Q4	es	Fair Value Of Securities Under Fair Value Option FairValueOfSecuritiesUnderFairValueOption	14200000	USD
CY2015	us-gaap	Fair Value Option Changes In Fair Value Gain Loss1 FairValueOptionChangesInFairValueGainLoss1	2000000	USD
CY2014	us-gaap	Fair Value Option Changes In Fair Value Gain Loss1 FairValueOptionChangesInFairValueGainLoss1	1900000	USD
CY2013	us-gaap	Fair Value Option Changes In Fair Value Gain Loss1 FairValueOptionChangesInFairValueGainLoss1	10200000	USD
CY2015Q4	us-gaap	Marketable Securities Restricted Noncurrent MarketableSecuritiesRestrictedNoncurrent	436900000	USD
CY2014Q4	us-gaap	Marketable Securities Restricted Noncurrent MarketableSecuritiesRestrictedNoncurrent	450800000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	33300000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	50200000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	56600000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	116400000	USD
CY2015Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	256500000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	33200000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	50700000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	57200000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	119300000	USD
CY2015Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	260400000	USD
CY2015Q4	us-gaap	Investments Fair Value Disclosure InvestmentsFairValueDisclosure	545700000	USD
CY2014Q4	us-gaap	Investments Fair Value Disclosure InvestmentsFairValueDisclosure	639200000	USD
CY2015	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	-18200000	USD
CY2015	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	26500000	USD
CY2015	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-11100000	USD
CY2015Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	430100000	USD
CY2013Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	424900000	USD
CY2014	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	1300000	USD
CY2014	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	25100000	USD
CY2014	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-5500000	USD
CY2014Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	426300000	USD
CY2014	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	-19500000	USD
CY2015Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	800000000	USD
CY2015	es	Short Term Debt Regulatory Limits ShortTermDebtRegulatoryLimits	The amount of short-term borrowings that may be incurred by CL&P, NSTAR Electric and WMECO is subject to periodic approval by the FERC. As a result of the NHPUC having jurisdiction over PSNH's short-term debt, PSNH is not currently required to obtain FERC approval for its short-term borrowings. On June 16, 2015, the FERC granted authorization that allows CL&P and WMECO to incur total short-term borrowings up to a maximum of $600 million and $300 million, respectively, effective January 1, 2016 through December 31, 2017. On June 11, 2014, the FERC granted authorization to allow NSTAR Electric to issue total short-term debt securities in an aggregate principal amount not to exceed $655 million outstanding at any one time, effective October 24, 2014 through October 23, 2016. CL&P's certificate of incorporation contains preferred stock provisions restricting the amount of unsecured debt that CL&P may incur, including limiting unsecured indebtedness with a maturity of less than 10 years to 10 percent of total capitalization. As of December 31, 2015, CL&P had $327.3 million of unsecured debt capacity available under this authorization. PSNH is authorized by regulation of the NHPUC to incur short-term borrowings up to 10 percent of net fixed plant plus an additional $60 million until further ordered by the NHPUC. As of December 31, 2015, PSNH's short-term debt authorization under the 10 percent of net fixed plant test plus $60 million totaled approximately $325 million.
CY2015	us-gaap	Line Of Credit Facility Description LineOfCreditFacilityDescription	Credit Agreements and Commercial Paper Programs: Eversource parent, CL&P, PSNH, WMECO, NSTAR Gas and Yankee Gas are parties to a five-year $1.45 billion revolving credit facility. On October 26, 2015, this revolving credit facility was amended and restated and the termination date was extended to September 4, 2020. Under the revolving credit facility, CL&P has a borrowing sublimit of $600 million, and PSNH and WMECO each have borrowing sublimits of $300 million. The revolving credit facility serves to backstop Eversource parent's $1.45 billion commercial paper program. The commercial paper program allows Eversource parent to issue commercial paper as a form of short-term debt. As of December 31, 2015 and 2014, Eversource parent had approximately $1.1 billion in short-term borrowings outstanding on each date under the Eversource parent commercial paper program, leaving $351.5 million and $348.9 million of available borrowing capacity as of December 31, 2015 and 2014, respectively. The weighted-average interest rate on these borrowings as of December 31, 2015 and 2014 was 0.72 percent and 0.43 percent, respectively. As of December 31, 2015, there were intercompany loans from Eversource parent of $277.4 million to CL&P, $231.3 million to PSNH and $143.4 million to WMECO. As of December 31, 2014, there were intercompany loans from Eversource parent of $133.4 million to CL&P, $90.5 million to PSNH and $21.4 million to WMECO. NSTAR Electric has a five-year $450 million revolving credit facility. On October 26, 2015, this revolving credit facility was amended and restated and the termination date was extended to September 4, 2020. The facility serves to backstop NSTAR Electric's $450 million commercial paper program. As of December 31, 2015 and 2014, NSTAR Electric had $62.5 million and $302 million, respectively, in short-term borrowings outstanding under its commercial paper program, leaving $387.5 million and $148 million of available borrowing capacity as of December 31, 2015 and 2014, respectively. The weighted-average interest rate on these borrowings as of December 31, 2015 and 2014 was 0.40 percent and 0.27 percent, respectively.
CY2015	es	Description Of St Debt Reclassified To Lt DescriptionOfStDebtReclassifiedToLt	On January 15, 2015, Eversource parent issued $150 million of 1.60 percent Series G Senior Notes due to mature in 2018 and $300 million of 3.15 percent Series H Senior Notes, due to mature in 2025. The proceeds, net of issuance costs, were used to repay short-term borrowings outstanding under the Eversource parent commercial paper program. As the debt proceeds, net of issuance costs, refinanced short-term debt, the short-term debt was classified as Long-Term Debt as of December 31, 2014.
CY2015Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	745000000	USD
CY2015Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	960000000	USD
CY2015Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	295000000	USD
CY2015Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	5736600000	USD
CY2015Q4	es	Longtermdebtmaturitiesrepaymentsofprincipaltotal Longtermdebtmaturitiesrepaymentsofprincipaltotal	8736600000	USD
CY2015Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	200000000	USD
CY2014Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	38.14
CY2015	es	Amount That Represents Deferred Regulatory Assets AmountThatRepresentsDeferredRegulatoryAssets	3200000	USD
CY2015	us-gaap	Defined Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year Description DefinedBenefitPlanEstimatedFutureEmployerContributionsInNextFiscalYearDescription	Eversource currently expects to make contributions of approximately $146 million in 2016, of which $21 million will be contributed by NSTAR Electric and $17 million by PSNH. The remaining $108 million is expected to be contributed by other Eversource subsidiaries, primarily Eversource Service. Eversource contributed $7.9 million to the PBOP Plan in 2015, of which $4.9 million was contributed by NSTAR Electric. Eversource expects to make approximately $9.5 million in contributions in 2016.
CY2015	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	30400000	USD
CY2014	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	29700000	USD
CY2013	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	37000000	USD
CY2015	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	7000000	USD
CY2014	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	22000000	USD
CY2015Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	8000000	shares
CY2015Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	3005010	shares
CY2014Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	3112020	shares
CY2015Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	469772	shares
CY2014Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	1024729	shares
CY2015Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	48.58
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	784376	shares
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	37.21
CY2015	es	Share Based Compensation Arrangement By Share Based Payment Award Vested Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardVestedOutstandingNumber	259536	shares
CY2015	es	Share Based Compensation Arrangement By Share Based Payment Award Expected To Vest ShareBasedCompensationArrangementByShareBasedPaymentAwardExpectedToVest	446283	shares
CY2015	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	23100000	USD
CY2014	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	24600000	USD
CY2013	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	27000000	USD
CY2015	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	9400000	USD
CY2014	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	10300000	USD
CY2013	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	10700000	USD
CY2015	es	Description Of Compensation Cost Not Yet Recognized Period For Recognition DescriptionOfCompensationCostNotYetRecognizedPeriodForRecognition	This cost is expected to be recognized ratably over a weighted-average period of 1.74 years for Eversource, and 1.73 years for each CL&P, NSTAR Electric, PSNH and WMECO.
CY2015Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	14900000	USD
CY2015	us-gaap	Employee Service Share Based Compensation Cash Received From Exercise Of Stock Options EmployeeServiceShareBasedCompensationCashReceivedFromExerciseOfStockOptions	4800000	USD
CY2015	us-gaap	Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions	1900000	USD
CY2015	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	33715	shares
CY2014	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	40779	shares
CY2015	es	Espp Discounted Purchase Price First Six Months EsppDiscountedPurchasePriceFirstSixMonths	52.8	USD
CY2015	es	Espp Discounted Purchase Price Second Six Months EsppDiscountedPurchasePriceSecondSixMonths	47.23	USD
CY2014	es	Espp Discounted Purchase Price First Six Months EsppDiscountedPurchasePriceFirstSixMonths	41.61	USD
CY2014	es	Espp Discounted Purchase Price Second Six Months EsppDiscountedPurchasePriceSecondSixMonths	41.71	USD
CY2015Q4	es	Employee Stock Purchase Plan Shares Remaining For Future Issuance EmployeeStockPurchasePlanSharesRemainingForFutureIssuance	743260	shares
CY2014Q4	es	Employee Stock Purchase Plan Shares Remaining For Future Issuance EmployeeStockPurchasePlanSharesRemainingForFutureIssuance	776975	shares
CY2014Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	351616	shares
CY2014Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	26.69
CY2014Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	9400000	USD
CY2015	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	-179744	shares
CY2015Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	171872	shares
CY2015	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	26.90
CY2015Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	26.47
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	4400000	USD
CY2015Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	4200000	USD
CY2015Q4	us-gaap	Deferred Compensation Cashbased Arrangements Liability Classified Noncurrent DeferredCompensationCashbasedArrangementsLiabilityClassifiedNoncurrent	55200000	USD
CY2014Q4	us-gaap	Deferred Compensation Cashbased Arrangements Liability Classified Noncurrent DeferredCompensationCashbasedArrangementsLiabilityClassifiedNoncurrent	57500000	USD
CY2013Q4	us-gaap	Deferred Compensation Cashbased Arrangements Liability Classified Noncurrent DeferredCompensationCashbasedArrangementsLiabilityClassifiedNoncurrent	51300000	USD
CY2015Q4	es	Deferred Compensation Cash Based Arrangements Expense Pertaining To Deferred Benefits DeferredCompensationCashBasedArrangementsExpensePertainingToDeferredBenefits	3900000	USD
CY2014Q4	es	Deferred Compensation Cash Based Arrangements Expense Pertaining To Deferred Benefits DeferredCompensationCashBasedArrangementsExpensePertainingToDeferredBenefits	4500000	USD
CY2013Q4	es	Deferred Compensation Cash Based Arrangements Expense Pertaining To Deferred Benefits DeferredCompensationCashBasedArrangementsExpensePertainingToDeferredBenefits	4400000	USD
CY2015	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	6200000	USD
CY2014	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	4400000	USD
CY2013	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	8800000	USD
CY2013	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	-9400000	USD
CY2014	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	24500000	USD
CY2015	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	45700000	USD
CY2015	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	51900000	USD
CY2014	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	28900000	USD
CY2013	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	-600000	USD
CY2013	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	386200000	USD
CY2014	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	406800000	USD
CY2015	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	436100000	USD
CY2015	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	55600000	USD
CY2014	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	36500000	USD
CY2013	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	45400000	USD
CY2013	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	-4100000	USD
CY2014	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	-3900000	USD
CY2015	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	-3600000	USD
CY2015	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	499100000	USD
CY2015	us-gaap	Income Tax Reconciliation Nondeductible Expense Depreciation IncomeTaxReconciliationNondeductibleExpenseDepreciation	-4600000	USD
CY2015	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	-3800000	USD
CY2015	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	61100000	USD
CY2015	us-gaap	Income Tax Rate Reconciliation Deductions Employee Stock Ownership Plan Dividends IncomeTaxRateReconciliationDeductionsEmployeeStockOwnershipPlanDividends	-8100000	USD
CY2015	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	4700000	USD
CY2015	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-4800000	USD
CY2014	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	453400000	USD
CY2014	us-gaap	Income Tax Reconciliation Nondeductible Expense Depreciation IncomeTaxReconciliationNondeductibleExpenseDepreciation	-5600000	USD
CY2014	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	-3500000	USD
CY2014	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	42500000	USD
CY2014	us-gaap	Income Tax Rate Reconciliation Deductions Employee Stock Ownership Plan Dividends IncomeTaxRateReconciliationDeductionsEmployeeStockOwnershipPlanDividends	-8000000	USD
CY2014	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-2900000	USD
CY2014	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-3700000	USD
CY2013	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	427200000	USD
CY2013	us-gaap	Income Tax Reconciliation Nondeductible Expense Depreciation IncomeTaxReconciliationNondeductibleExpenseDepreciation	-7400000	USD
CY2013	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	-3700000	USD
CY2013	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	27600000	USD
CY2013	us-gaap	Income Tax Rate Reconciliation Deductions Employee Stock Ownership Plan Dividends IncomeTaxRateReconciliationDeductionsEmployeeStockOwnershipPlanDividends	-8000000	USD
CY2013	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-4300000	USD
CY2013	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-400000	USD
CY2015	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.379	pure
CY2014	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.362	pure
CY2013	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.350	pure
CY2015Q4	us-gaap	Deferred Tax Assets Derivative Instruments DeferredTaxAssetsDerivativeInstruments	172700000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Derivative Instruments DeferredTaxAssetsDerivativeInstruments	199600000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	243500000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	366700000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	637500000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	632200000	USD
CY2014Q4	es	Deferred Tax Assets Tax Effect Tax Regulatory Liabilities DeferredTaxAssetsTaxEffectTaxRegulatoryLiabilities	10000000	USD
CY2015Q4	es	Deferred Tax Assets Tax Effect Tax Regulatory Liabilities DeferredTaxAssetsTaxEffectTaxRegulatoryLiabilities	9700000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	197100000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	198700000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	3700000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	5100000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	1647900000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	1442000000	USD
CY2015Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	4602600000	USD
CY2015Q4	es	Deferred Tax Liabilities Regulatory Assets Other Regulatory Deferrals DeferredTaxLiabilitiesRegulatoryAssetsOtherRegulatoryDeferrals	1289100000	USD
CY2014Q4	es	Deferred Tax Liabilities Regulatory Assets Other Regulatory Deferrals DeferredTaxLiabilitiesRegulatoryAssetsOtherRegulatoryDeferrals	1277900000	USD
CY2014Q4	es	Deferred Tax Liabilities Regulatory Assets Tax Effect Tax Regulatory Assets DeferredTaxLiabilitiesRegulatoryAssetsTaxEffectTaxRegulatoryAssets	240200000	USD
CY2015Q4	es	Deferred Tax Liabilities Regulatory Assets Tax Effect Tax Regulatory Assets DeferredTaxLiabilitiesRegulatoryAssetsTaxEffectTaxRegulatoryAssets	249300000	USD
CY2015Q4	es	Deferred Tax Liabilities Regulatory Assets Derivative Assets DeferredTaxLiabilitiesRegulatoryAssetsDerivativeAssets	17700000	USD
CY2014Q4	es	Deferred Tax Liabilities Regulatory Assets Derivative Assets DeferredTaxLiabilitiesRegulatoryAssetsDerivativeAssets	32600000	USD
CY2014Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	196300000	USD
CY2015Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	159400000	USD
CY2015Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	6589700000	USD
CY2014Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	6275700000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	1445700000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	1653000000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	60500000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	60500000	USD
CY2015Q4	es	Deferred Tax Liabilities Resulting From Property Tax Accruals And Other DeferredTaxLiabilitiesResultingFromPropertyTaxAccrualsAndOther	76700000	USD
CY2014Q4	es	Deferred Tax Liabilities Resulting From Property Tax Accruals And Other DeferredTaxLiabilitiesResultingFromPropertyTaxAccrualsAndOther	109600000	USD
CY2014Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	4215900000	USD
CY2015Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	5400000	USD
CY2014Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	59100000	USD
CY2015Q4	es	Purchase Accounting Deferred Tax Asset PurchaseAccountingDeferredTaxAsset	119300000	USD
CY2014Q4	es	Purchase Accounting Deferred Tax Asset PurchaseAccountingDeferredTaxAsset	126200000	USD
CY2015Q4	es	Deferred Tax Liabilities Goodwill Regulatory Asset DeferredTaxLiabilitiesGoodwillRegulatoryAsset	194900000	USD
CY2014Q4	es	Deferred Tax Liabilities Goodwill Regulatory Asset DeferredTaxLiabilitiesGoodwillRegulatoryAsset	203200000	USD
CY2015	us-gaap	Tax Credit Carryforward Description TaxCreditCarryforwardDescription	In 2015, the Company decreased its valuation allowance reserve for state credits and state loss carryforwards by $1.3 million (CL&P $0.9 million), net of tax, to reflect an update for expired state tax credits and loss carryforwards. In 2014, the Company recorded a reduction to its state credit carryforwards of $11 million (CL&P $10.1 million), net of tax, as a result of an update to reflect the amounts expired. Further, the Company decreased its valuation allowance reserve for state credits by $19.2 million at CL&P, net of tax, to reflect an update for expired state credits and latest estimate of usage.
CY2015Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	48000000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	83100000	USD
CY2014	us-gaap	Other Information Pertaining To Income Taxes OtherInformationPertainingToIncomeTaxes	2014 Federal Legislation: On December 19, 2014, the "Tax Increase Prevention Act of 2014" became law, which extended the accelerated deduction of depreciation to businesses through 2014. This extended stimulus provided Eversource with cash flow benefits of approximately $250 million (approximately $86 million at CL&P, $64 million at NSTAR Electric, $44 million at PSNH, and $21 million at WMECO) in 2015.
CY2015	us-gaap	Significant Change In Unrecognized Tax Benefits Is Reasonably Possible Other Information SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleOtherInformation	Eversource estimates that during the next twelve months, differences of a non-timing nature could be resolved, resulting in a zero to $2.3 million decrease in unrecognized tax benefits by Eversource. These estimated changes are not expected to have a material impact on the earnings of Eversource. Other companies' impacts are not expected to be material.
CY2013	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	8200000	USD
CY2013Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	38200000	USD
CY2013	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	-1100000	USD
CY2014	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	9300000	USD
CY2014Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	46200000	USD
CY2014	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	-1600000	USD
CY2013	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	-49800000	USD
CY2013	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	-2200000	USD
CY2014	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	300000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	9900000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	100000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	-8200000	USD
CY2014	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	400000	USD
CY2013	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	-8600000	USD
CY2015Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	2000000	USD
CY2014Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	1900000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	100000	USD
CY2015	us-gaap	Income Tax Examination Description IncomeTaxExaminationDescription	Tax Positions: During 2015 and 2014, Eversource did not resolve any of its uncertain tax positions.
CY2015	us-gaap	Other Information Pertaining To Income Taxes OtherInformationPertainingToIncomeTaxes	2015 Federal Legislation: On December 18, 2015, the "Protecting Americans from Tax Hikes" Act became law, which extended the accelerated deduction of depreciation to businesses from 2015 through 2019. This extended stimulus provides Eversource with cash flow benefits in 2016 of approximately $275 million (including approximately $105 million for CL&P, $72 million for NSTAR Electric, $46 million for PSNH, and $25 million for WMECO) due to a refund of taxes paid in 2015 and lower expected tax payments in 2016 of approximately $300 million. 2015 Connecticut Legislation: In 2015, the state of Connecticut enacted several changes to its corporate tax laws. Among the changes, commencing as of January 1, 2015, is the reduction in the amount of tax credits that corporations can utilize against its tax liability in a year and a continuation of the corporate income tax surcharge through 2018, which effectively increases the state corporate tax rate to 9 percent for the years 2016 and 2017 and 8.25 percent for 2018. Also, effective January 1, 2016, all Connecticut companies have a mandatory unitary tax filing requirement. Management continues to review the tax law changes and their impact on the effective tax rates of Eversource and CL&P.
CY2013Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	35400000	USD
CY2014	us-gaap	Accrual For Environmental Loss Contingencies Provision For New Losses AccrualForEnvironmentalLossContingenciesProvisionForNewLosses	12700000	USD
CY2014	us-gaap	Accrual For Environmental Loss Contingencies Payments AccrualForEnvironmentalLossContingenciesPayments	4800000	USD
CY2014Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	43300000	USD
CY2015	us-gaap	Accrual For Environmental Loss Contingencies Provision For New Losses AccrualForEnvironmentalLossContingenciesProvisionForNewLosses	13500000	USD
CY2015	us-gaap	Accrual For Environmental Loss Contingencies Payments AccrualForEnvironmentalLossContingenciesPayments	5700000	USD
CY2015Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	51100000	USD
CY2015	es	Environmental Site Quantity EnvironmentalSiteQuantity	64	pure
CY2014	es	Environmental Site Quantity EnvironmentalSiteQuantity	65	pure
CY2015	us-gaap	Site Contingency Environmental Remediation Costs Recognized SiteContingencyEnvironmentalRemediationCostsRecognized	CERCLA: Of the total environmental sites, nine sites (four for NSTAR Electric and three for PSNH) are superfund sites under the federal Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) and its amendments or state equivalents for which the Company has been notified that it is a potentially responsible party but for which the site assessment and remediation are not being managed by the Company.  As of December 31, 2015, a liability of $0.8 million accrued on these sites represents management's best estimate of its potential remediation costs with respect to these superfund sites. Included in the Eversource number of sites and reserve amounts above are former MGP sites that were operated several decades ago and manufactured gas from coal and other processes, which resulted in certain by-products remaining in the environment that may pose a potential risk to human health and the environment, for which Eversource may have potential liability. The reserve balances related to these former MGP sites were $45.5 million and $38.8 million as of December 31, 2015 and 2014, respectively, and related primarily to the natural gas business segment. As of December 31, 2015, for 9 environmental sites (3 for CL&P, 1 for WMECO) that are included in the Company's reserve for environmental costs, the information known and the nature of the remediation options allow for the Company to estimate the range of losses for environmental costs. As of December 31, 2015, $24.7 million (including $1.7 million for CL&P and $0.3 million for WMECO) had been accrued as a liability for these sites, which represents the low end of the range of the liabilities for environmental costs. Management believes that additional losses of up to approximately $33.9 million (approximately $1.4 million for CL&P, and $0.1 million for WMECO) may be incurred in remediating these sites. As of December 31, 2015, for 12 environmental sites (3 for CL&P and 2 for NSTAR Electric) that are included in the Company’s reserve for environmental costs, management cannot reasonably estimate the exposure to loss in excess of the reserve, or range of loss, as these sites are under investigation and/or there is significant uncertainty as to what remedial actions, if any, the Company may be required to undertake. As of December 31, 2015, $13.7 million (including $2 million for CL&P) had been accrued as a liability for these sites. As of December 31, 2015, for the remaining 43 environmental sites (including 8 for CL&P, 13 for NSTAR Electric, 12 for PSNH, and 3 for WMECO) that are included in the Company’s reserve for environmental costs, the $12.7 million accrual (including $0.9 million for CL&P, $2.4 million for NSTAR Electric, $4.5 million for PSNH, and $0.3 million for WMECO) represents management’s best estimate of the potential liability and no additional loss is anticipated at this time.
CY2015Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Third Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary	442300000	USD
CY2015Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Fourth Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary	376200000	USD
CY2015Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Fifth Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary	344900000	USD
CY2015Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Due After Five Years UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears	2371700000	USD
CY2015Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance Sheet Amount UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount	4810200000	USD
CY2015Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On First Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary	684500000	USD
CY2015Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Second Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary	590600000	USD
CY2014	es	Supply And Stranded Costs Obligations Incurred SupplyAndStrandedCostsObligationsIncurred	99200000	USD
CY2015	es	Supply And Stranded Costs Obligations Incurred SupplyAndStrandedCostsObligationsIncurred	147600000	USD
CY2013	es	Supply And Stranded Costs Obligations Incurred SupplyAndStrandedCostsObligationsIncurred	141000000	USD
CY2015	es	Peaker Cfd Expense Incurred PeakerCfdExpenseIncurred	42700000	USD
CY2014	es	Peaker Cfd Expense Incurred PeakerCfdExpenseIncurred	18100000	USD
CY2013	es	Peaker Cfd Expense Incurred PeakerCfdExpenseIncurred	51900000	USD
CY2015	es	Natural Gas Procurement Costs Incurred NaturalGasProcurementCostsIncurred	428600000	USD
CY2014	es	Natural Gas Procurement Costs Incurred NaturalGasProcurementCostsIncurred	482500000	USD
CY2013	es	Natural Gas Procurement Costs Incurred NaturalGasProcurementCostsIncurred	349800000	USD
CY2013	es	Fuel Costs Incurred FuelCostsIncurred	112600000	USD
CY2014	es	Fuel Costs Incurred FuelCostsIncurred	120500000	USD
CY2015	es	Fuel Costs Incurred FuelCostsIncurred	95900000	USD
CY2015	es	Transmission Support Commitment Costs Incurred TransmissionSupportCommitmentCostsIncurred	25300000	USD
CY2014	es	Transmission Support Commitment Costs Incurred TransmissionSupportCommitmentCostsIncurred	25000000	USD
CY2013	es	Transmission Support Commitment Costs Incurred TransmissionSupportCommitmentCostsIncurred	24900000	USD
CY2015	es	Renewable Energy Costs Incurred RenewableEnergyCostsIncurred	144300000	USD
CY2014	es	Renewable Energy Costs Incurred RenewableEnergyCostsIncurred	114400000	USD
CY2013	es	Renewable Energy Costs Incurred RenewableEnergyCostsIncurred	91300000	USD
CY2015	es	Myapc Phase One Damages Proceeds To Member Companies MyapcPhaseOneDamagesProceedsToMemberCompanies	In accordance with MYAPC's three-year refund plan of the DOE Phase I Damages proceeds, in September 2014, MYAPC returned the second portion of the proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, in the amount of $3.2 million, $1.1 million, $1.4 million and $0.8 million, respectively. On September 28, 2015, MYAPC returned the remaining DOE Phase I Damages proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, in the amount of $2.3 million, $0.8 million, $1 million and $0.6 million, respectively. These amounts reduced receivables at CL&P, NSTAR Electric, PSNH and WMECO.
CY2014	es	Refund Obligation To Customers RefundObligationToCustomers	As of December 31, 2014, CL&P's refund obligation to customers of $65.4 million was recorded as an offset to the deferred storm restoration costs regulatory asset, as directed by PURA. NSTAR Electric's, PSNH's and WMECO's refund obligation to customers of $29.1 million, $13.1 million and $18.1 million, respectively, was recorded as a regulatory liability in each company's respective regulatory tracker mechanisms. Refunds to customers for these Phase II DOE proceeds were completed in 2015.
CY2015	us-gaap	Loss Contingency Managements Assessment And Process LossContingencyManagementsAssessmentAndProcess	E.         FERC ROE Complaints E.         FERC ROE Complaints Three separate complaints have been filed at FERC by combinations of New England state attorneys general, state regulatory commissions, consumer advocates, consumer groups, municipal parties and other parties (the "Complainants"). In the first complaint, filed in 2011, the Complainants alleged that the NETOs' base ROE that had been utilized since 2006 was unjust and unreasonable, asserted that the rate was excessive due to changes in the capital markets, and sought an order to reduce it prospectively from the date of the final FERC order and for the 15-month period beginning October 1, 2011 to December 31, 2012. In the second and third complaints, filed in 2012 and 2014, the Complainants challenged the NETOs' base ROE and sought refunds for the respective 15-month periods beginning December 27, 2012 and July 31, 2014. As a result of the actions taken by the FERC and other developments in the first complaint matter, the Company recorded additional reserves at its electric subsidiaries in 2015 and 2014. In 2015, Eversource recognized a pre-tax charge to earnings (excluding interest) of $20 million, of which $12.5 million was recorded at CL&P, $2.4 million at NSTAR Electric, $1 million at PSNH, and $4.1 million at WMECO. The pre-tax charge was recorded as a regulatory liability and as a reduction to Operating Revenues. In 2014, the net aggregate pre-tax charge to earnings (excluding interest) totaled $37 million, of which $20.7 million was recorded at CL&P, $7.9 million at NSTAR Electric, $2.8 million at PSNH and $5.6 million at WMECO. In 2013, the net aggregate pre-tax charge to earnings (excluding interest) totaled $23.7 million, of which $12.8 million was recorded at CL&P, $5.7 million at NSTAR Electric, $2.3 million at PSNH and $2.9 million at WMECO. The second and third complaint proceedings are ongoing and a final FERC order is expected in late 2016 or early 2017. Although management is uncertain on the final outcome of the second and third complaints regarding the ROE, management believes the current reserves established are appropriate to reflect probable and reasonably estimable refunds. F.        NSTAR Electric and NSTAR Gas Comprehensive Settlement Agreement On March 2, 2015, the DPU approved the comprehensive settlement agreement between NSTAR Electric, NSTAR Gas and the Massachusetts Attorney General (the "Settlement") as filed with the DPU on December 31, 2014. The Settlement resolved the outstanding NSTAR Electric CPSL program filings for 2006 through 2011, the NSTAR Electric and NSTAR Gas PAM and energy efficiency-related customer billing adjustments reported in 2012, and the recovery of LBR related to NSTAR Electric's energy efficiency programs for 2009 through 2011 (11 dockets in total). In the first quarter of 2015, as a result of the DPU order, NSTAR Electric and NSTAR Gas commenced refunding a combined $44.7 million to customers, which was recorded as a regulatory liability. Refunds to customers will continue through December 2016. As a result of the Settlement, NSTAR Electric increased its operating revenues and decreased its amortization expense in 2015, resulting in the recognition of a $21.7 million pre-tax benefit in 2015. G.        NSTAR Electric Basic Service Bad Debt Adder On January 7, 2015, the DPU issued an order concluding that NSTAR Electric had removed energy-related bad debt costs from base distribution rates effective January 1, 2006. As a result of the DPU order, in the first quarter of 2015, NSTAR Electric increased its regulatory assets and reduced its operations and maintenance expense by an under recovered amount of $24.2 million for energy-related bad debt costs through 2014, resulting in a pre-tax benefit in 2015. NSTAR Electric filed for recovery of the energy-related bad debt costs regulatory asset from customers and on November 20, 2015the DPU approved NSTAR Electric’s proposed rate increase, to recover these costs over a 12-month period, effective January 1, 2016. H.        PSNH Generation Restructuring On June 10, 2015, Eversource and PSNH entered into the 2015 Public Service Company of New Hampshire Restructuring and Rate Stabilization Agreement (the Agreement) with the New Hampshire Office of Energy and Planning, certain members of the NHPUC staff, the Office of Consumer Advocate, two State Senators, and several other parties. The Agreement was filed with the NHPUC on the same day. Under the terms of the Agreement, PSNH has agreed to divest its generation assets upon NHPUC approval. The Agreement is designed to provide a resolution of issues pertaining to PSNH's generation assets in pending regulatory proceedings before the NHPUC. The Agreement provided for the Clean Air Project prudence proceeding to be resolved and all remaining Clean Air Project costs to be included in rates effective January 1, 2016. As part of the Agreement, PSNH has agreed to forego recovery of $25 million of the deferred equity return related to the Clean Air Project. In addition, PSNH will not seek a general distribution rate increase effective before July 1, 2017 and will contribute $5 million to create a clean energy fund, which will not be recoverable from its customers. In 2015, PSNH recorded the $5 million contribution as a long-term liability and an increase to Operations and Maintenance expense on the statements of income. Upon completion of the divestiture process, all remaining stranded costs will be recovered via bonds that will be secured by a non-bypassable charge or through other recoveries in rates billed to PSNH customers. On January 26, 2016, Advisory Staff of the NHPUC and the parties to the Agreement filed a stipulation with the NHPUC agreeing that near-term divestiture of PSNH’s generation was in the public interest and that the Agreement should be approved. Implementation of the Agreement is subject to NHPUC approval, which is expected in early 2016. If the NHPUC approves the settlements and the sale of the plants, then management expects to sell the plants in the first half of 2017. The sales price of the generating assets could be less than the carrying value, but we believe that full recovery of PSNH's generation assets is probable through a combination of cash flows during the remaining operating period, sales proceeds upon divestiture, and recovery of stranded costs in future rates. I.        Litigation and Legal Proceedings Eversource, including CL&P, NSTAR Electric, PSNH and WMECO, are involved in legal, tax and regulatory proceedings regarding matters arising in the ordinary course of business, which involve management's assessment to determine the probability of whether a loss will occur and, if probable, its best estimate of probable loss. The Company records and discloses losses when these losses are probable and reasonably estimable, and discloses matters when losses are probable but not estimable or when losses are reasonably possible. Legal costs related to the defense of loss contingencies are expensed as incurred.
CY2015	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	16300000	USD
CY2015Q4	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	16400000	USD
CY2015Q4	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	13800000	USD
CY2015Q4	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	10400000	USD
CY2015Q4	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	8500000	USD
CY2015Q4	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	15400000	USD
CY2015Q4	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	71300000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Due In Two Years CapitalLeasesFutureMinimumPaymentsDueInTwoYears	2200000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Due In Three Years CapitalLeasesFutureMinimumPaymentsDueInThreeYears	2100000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Due In Four Years CapitalLeasesFutureMinimumPaymentsDueInFourYears	2100000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Due In Five Years CapitalLeasesFutureMinimumPaymentsDueInFiveYears	2000000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Due Thereafter CapitalLeasesFutureMinimumPaymentsDueThereafter	1400000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Due CapitalLeasesFutureMinimumPaymentsDue	11800000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Interest Included In Payments CapitalLeasesFutureMinimumPaymentsInterestIncludedInPayments	3600000	USD
CY2015Q4	us-gaap	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPayments	8200000	USD
CY2013Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-46000000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	900000	USD
CY2014	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-33900000	USD
CY2014	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-5900000	USD
CY2015	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-6300000	USD
CY2015	us-gaap	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths	3500000	USD
CY2015	es	Pension Serp And Pbop Gain Loss To Be Reclassified Within Twelve Months PensionSerpAndPbopGainLossToBeReclassifiedWithinTwelveMonths	6900000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Before Reclassification Adjustments Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax	2000000	USD
CY2014	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Before Reclassification Adjustments Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax	-22300000	USD
CY2013	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Before Reclassification Adjustments Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax	11400000	USD
CY2014Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	333359172	shares
CY2015Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	333862615	shares
CY2015Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	380000000	shares
CY2015Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	16671366	shares
CY2014Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	16375835	shares
CY2014Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	5
CY2014Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	380000000	shares
CY2015Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	317191249	shares
CY2014Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	316983337	shares
CY2015	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	532521	shares
CY2015	us-gaap	Line Of Credit Facility Dividend Restrictions LineOfCreditFacilityDividendRestrictions	CL&P, NSTAR Electric, PSNH and WMECO are subject to Section 305 of the Federal Power Act that makes it unlawful for a public utility to make or pay a dividend from any funds "properly included in its capital account." Management believes that this Federal Power Act restriction, as applied to CL&P, NSTAR Electric, PSNH and WMECO, would not be construed or applied by the FERC to prohibit the payment of dividends from retained earnings for lawful and legitimate business purposes. In addition, certain state statutes may impose additional limitations on such companies and on Yankee Gas and NSTAR Gas. Such state law restrictions do not restrict the payment of dividends from retained earnings or net income. Pursuant to the joint revolving credit agreement of Eversource, CL&P, PSNH, WMECO, Yankee Gas and NSTAR Gas, and to the NSTAR Electric revolving credit agreement, each company is required to maintain consolidated total debt to total capitalization ratio of no greater than 65 percent at the end of each fiscal quarter. As of December 31, 2015, all companies were in compliance with such covenant. The Retained Earnings balances subject to these restrictions were $2.8 billion for Eversource, $1.2 billion for CL&P, $1.6 billion for NSTAR Electric, $494.9 million for PSNH and $198.1 million for WMECO as of December 31, 2015. As of December 31, 2015, Eversource, CL&P, NSTAR Electric, PSNH, WMECO, Yankee Gas and NSTAR Gas were in compliance with all such provisions of the revolving credit agreements that may restrict the payment of dividends.
CY2015Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	5
CY2015	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	26.02
CY2015Q4	us-gaap	Preferred Stock Value Outstanding PreferredStockValueOutstanding	155600000	USD
CY2014Q4	us-gaap	Preferred Stock Value Outstanding PreferredStockValueOutstanding	155600000	USD
CY2015	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	1095806	shares
CY2014	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	1280666	shares
CY2013	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	899773	shares
CY2015	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.77
CY2014	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.59
CY2013	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.49
CY2015	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.76
CY2014	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.58
CY2013	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.49
CY2015	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	317336881	shares
CY2015	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	318432687	shares
CY2014	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	316136748	shares
CY2014	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	317417414	shares
CY2013	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	315311387	shares
CY2013	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	316211160	shares
CY2015	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1474	shares
CY2014	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	3643	shares
CY2013	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1575	shares
CY2015Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	497500000	USD
CY2015Q1	us-gaap	Net Income Loss NetIncomeLoss	255100000	USD
CY2014Q1	us-gaap	Revenues Revenues	2290600000	USD
CY2014Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	467700000	USD
CY2014Q1	us-gaap	Net Income Loss NetIncomeLoss	237800000	USD
CY2014Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	236000000	USD
CY2015Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	253300000	USD
CY2012	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	3200000000	USD
CY2015Q2	us-gaap	Revenues Revenues	1817100000	USD
CY2015Q3	us-gaap	Revenues Revenues	1933100000	USD
CY2015Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	469200000	USD
CY2015Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	412000000	USD
CY2015Q2	us-gaap	Net Income Loss NetIncomeLoss	209400000	USD
CY2015Q3	us-gaap	Net Income Loss NetIncomeLoss	237800000	USD
CY2015Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	235900000	USD
CY2015Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	207500000	USD
CY2014Q2	us-gaap	Revenues Revenues	1677600000	USD
CY2014Q3	us-gaap	Revenues Revenues	1892500000	USD
CY2014Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	440900000	USD
CY2014Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	294000000	USD
CY2014Q2	us-gaap	Net Income Loss NetIncomeLoss	129200000	USD
CY2014Q3	us-gaap	Net Income Loss NetIncomeLoss	236500000	USD
CY2014Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	234600000	USD
CY2014Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	127400000	USD
CY2015Q1	us-gaap	Revenues Revenues	2513400000	USD
CY2015Q4	us-gaap	Revenues Revenues	1691200000	USD
CY2015Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	385500000	USD
CY2015Q4	us-gaap	Net Income Loss NetIncomeLoss	183700000	USD
CY2015Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	181800000	USD
CY2014Q4	us-gaap	Revenues Revenues	1881200000	USD
CY2014Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	430200000	USD
CY2014Q4	us-gaap	Net Income Loss NetIncomeLoss	223600000	USD
CY2014Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	221500000	USD
CY2015Q1	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.80
CY2015Q2	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.65
CY2015Q3	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.74
CY2015Q4	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.57
CY2014Q4	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.69
CY2014Q3	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.74
CY2014Q2	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.40
CY2014Q1	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.75
CY2014	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	55657000	USD
CY2013	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	55465000	USD
CY2014	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	102818000	USD
CY2013	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	87507000	USD
CY2012Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	165549000	USD
CY2013Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	171251000	USD
CY2014	us-gaap	Valuation Allowances And Reserves Charged To Other Accounts ValuationAllowancesAndReservesChargedToOtherAccounts	51227000	USD
CY2013	us-gaap	Valuation Allowances And Reserves Charged To Other Accounts ValuationAllowancesAndReservesChargedToOtherAccounts	37744000	USD
CY2013Q4	es	Uncollectible Hardship Accounts Receivable Reserves UncollectibleHardshipAccountsReceivableReserves		USD
CY2014Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	175317000	USD
CY2015	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	51077000	USD
CY2015	us-gaap	Valuation Allowances And Reserves Charged To Other Accounts ValuationAllowancesAndReservesChargedToOtherAccounts	79622000	USD
CY2015	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	115336000	USD
CY2015Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	190680000	USD
CY2015	dei	Entity Registrant Name EntityRegistrantName	EVERSOURCE ENERGY
CY2015	dei	Document Type DocumentType	10-K
CY2015	dei	Document Period End Date DocumentPeriodEndDate	2015-12-31
CY2015	dei	Entity Central Index Key EntityCentralIndexKey	0000072741
CY2015	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2016Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	317191249	shares
CY2015Q2	dei	Entity Public Float EntityPublicFloat	14345789335	USD
CY2015	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2015	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2015	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2015	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2015	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2015
CY2015	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2015	dei	Amendment Flag AmendmentFlag	false
CY2015Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	295243000	USD
CY2014Q4	us-gaap	Assets Assets	29740387000	USD
CY2014Q4	us-gaap	Notes Payable NotesPayable	956825000	USD
CY2014Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	312369000	USD
CY2015Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	305359000	USD
CY2014Q4	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	18647041000	USD
CY2014Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	337307000	USD

Files In Submission

Name	View Source	Status
0000072741-16-000063-index-headers.html	Edgar Link	pending
0000072741-16-000063-index.html	Edgar Link	pending
0000072741-16-000063.txt	Edgar Link	pending
0000072741-16-000063-xbrl.zip	Edgar Link	pending
amdratestabsettagrmnt.htm	Edgar Link	pending
es-20151231.xml	Edgar Link	completed
es-20151231.xsd	Edgar Link	pending
es-20151231_cal.xml	Edgar Link	unprocessable
es-20151231_def.xml	Edgar Link	unprocessable
es-20151231_lab.xml	Edgar Link	unprocessable
es-20151231_pre.xml	Edgar Link	unprocessable
eversourceagrmnt.htm	Edgar Link	pending
eversourceandallsubsconsents.htm	Edgar Link	pending
eversourcedeferredcompplan.htm	Edgar Link	pending
eversourceenergyserps.htm	Edgar Link	pending
exhbit103trusteecomp.htm	Edgar Link	pending
exhibit12clp.htm	Edgar Link	pending
exhibit12es.htm	Edgar Link	pending
exhibit12nstarelectric.htm	Edgar Link	pending
exhibit12psnh.htm	Edgar Link	pending
exhibit12wmeco.htm	Edgar Link	pending
exhibit21.htm	Edgar Link	pending
exhibit311clp.htm	Edgar Link	pending
exhibit311es.htm	Edgar Link	pending
exhibit311nstarelectric.htm	Edgar Link	pending
exhibit311psnh.htm	Edgar Link	pending
exhibit311wmeco.htm	Edgar Link	pending
exhibit31clp.htm	Edgar Link	pending
exhibit31es.htm	Edgar Link	pending
exhibit31nstarelectric.htm	Edgar Link	pending
exhibit31psnh.htm	Edgar Link	pending
exhibit31wmeco.htm	Edgar Link	pending
exhibit32clp.htm	Edgar Link	pending
exhibit32es.htm	Edgar Link	pending
exhibit32nstarelectric.htm	Edgar Link	pending
exhibit32psnh.htm	Edgar Link	pending
exhibit32wmeco.htm	Edgar Link	pending
f2015form10k.htm	Edgar Link	pending
f2015form10k001.jpg	Edgar Link	pending
f2015form10k003.gif	Edgar Link	pending
f2015form10k004.jpg	Edgar Link	pending
f2015form10k005.jpg	Edgar Link	pending
f2015form10k006.jpg	Edgar Link	pending
f2015form10k007.jpg	Edgar Link	pending
f2015form10k008.jpg	Edgar Link	pending
f2015form10k009.jpg	Edgar Link	pending
f2015form10k010.jpg	Edgar Link	pending
f2015form10k011.jpg	Edgar Link	pending
f2015form10k012.jpg	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
nstarcreditagrmnt.htm	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
R100.htm	Edgar Link	pending
R101.htm	Edgar Link	pending
R102.htm	Edgar Link	pending
R103.htm	Edgar Link	pending
R104.htm	Edgar Link	pending
R105.htm	Edgar Link	pending
R106.htm	Edgar Link	pending
R11.htm	Edgar Link	pending
R12.htm	Edgar Link	pending
R13.htm	Edgar Link	pending
R14.htm	Edgar Link	pending
R15.htm	Edgar Link	pending
R16.htm	Edgar Link	pending
R17.htm	Edgar Link	pending
R18.htm	Edgar Link	pending
R19.htm	Edgar Link	pending
R2.htm	Edgar Link	pending
R20.htm	Edgar Link	pending
R21.htm	Edgar Link	pending
R22.htm	Edgar Link	pending
R23.htm	Edgar Link	pending
R24.htm	Edgar Link	pending
R25.htm	Edgar Link	pending
R26.htm	Edgar Link	pending
R27.htm	Edgar Link	pending
R28.htm	Edgar Link	pending
R29.htm	Edgar Link	pending
R3.htm	Edgar Link	pending
R30.htm	Edgar Link	pending
R31.htm	Edgar Link	pending
R32.htm	Edgar Link	pending
R33.htm	Edgar Link	pending
R34.htm	Edgar Link	pending
R35.htm	Edgar Link	pending
R36.htm	Edgar Link	pending
R37.htm	Edgar Link	pending
R38.htm	Edgar Link	pending
R39.htm	Edgar Link	pending
R4.htm	Edgar Link	pending
R40.htm	Edgar Link	pending
R41.htm	Edgar Link	pending
R42.htm	Edgar Link	pending
R43.htm	Edgar Link	pending
R44.htm	Edgar Link	pending
R45.htm	Edgar Link	pending
R46.htm	Edgar Link	pending
R47.htm	Edgar Link	pending
R48.htm	Edgar Link	pending
R49.htm	Edgar Link	pending
R5.htm	Edgar Link	pending
R50.htm	Edgar Link	pending
R51.htm	Edgar Link	pending
R52.htm	Edgar Link	pending
R53.htm	Edgar Link	pending
R54.htm	Edgar Link	pending
R55.htm	Edgar Link	pending
R56.htm	Edgar Link	pending
R57.htm	Edgar Link	pending
R58.htm	Edgar Link	pending
R59.htm	Edgar Link	pending
R6.htm	Edgar Link	pending
R60.htm	Edgar Link	pending
R61.htm	Edgar Link	pending
R62.htm	Edgar Link	pending
R63.htm	Edgar Link	pending
R64.htm	Edgar Link	pending
R65.htm	Edgar Link	pending
R66.htm	Edgar Link	pending
R67.htm	Edgar Link	pending
R68.htm	Edgar Link	pending
R69.htm	Edgar Link	pending
R7.htm	Edgar Link	pending
R70.htm	Edgar Link	pending
R71.htm	Edgar Link	pending
R72.htm	Edgar Link	pending
R73.htm	Edgar Link	pending
R74.htm	Edgar Link	pending
R75.htm	Edgar Link	pending
R76.htm	Edgar Link	pending
R77.htm	Edgar Link	pending
R78.htm	Edgar Link	pending
R79.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R80.htm	Edgar Link	pending
R81.htm	Edgar Link	pending
R82.htm	Edgar Link	pending
R83.htm	Edgar Link	pending
R84.htm	Edgar Link	pending
R85.htm	Edgar Link	pending
R86.htm	Edgar Link	pending
R87.htm	Edgar Link	pending
R88.htm	Edgar Link	pending
R89.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
R90.htm	Edgar Link	pending
R91.htm	Edgar Link	pending
R92.htm	Edgar Link	pending
R93.htm	Edgar Link	pending
R94.htm	Edgar Link	pending
R95.htm	Edgar Link	pending
R96.htm	Edgar Link	pending
R97.htm	Edgar Link	pending
R98.htm	Edgar Link	pending
R99.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending
transmittalletter2015001.jpg	Edgar Link	pending

Create your account

Find Stocks Worth Researching

Deeply Understand Businesses

Value Businesses Intelligently

$ES
EVERSOURCE ENERGY Stock $es

2014 Q4 Form 10-K Financial Statement

#000007274116000063 Filed on February 26, 2016

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ES EVERSOURCE ENERGY Stock $es

2014 Q4 Form 10-K Financial Statement

#000007274116000063 Filed on February 26, 2016

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ES
EVERSOURCE ENERGY Stock $es