PSNH GENERATION ASSET SALE - PSNH Generation Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Gross Plant	$ 26,289,100	$ 25,226,600
Accumulated Depreciation	(6,728,100)	(6,396,700)
Net Plant	20,807,943	19,892,441
Fuel, Materials, Supplies and Allowances	311,051	336,476
Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Gross Plant	4,106,700	3,891,100
Accumulated Depreciation	(1,243,800)	(1,171,000)
Net Plant	2,973,057	2,855,363
Fuel, Materials, Supplies and Allowances	160,882	$ 156,868
Electricity Generation Plant, Non-Nuclear [Member] | Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Gross Plant	1,191,000
Accumulated Depreciation	(552,100)
Net Plant	638,900
Fuel, Materials, Supplies and Allowances	$ 161,900