CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Income	$ 995,515	$ 949,821	$ 886,004
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	1,974	2,137	2,079
Changes in Unrealized (Losses)/Gains on Marketable Securities	(350)	2,294	(2,588)
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	(2,745)	(2,869)	7,674
Other Comprehensive (Loss)/Income, Net of Tax	(1,121)	1,562	7,165
Comprehensive Income Attributable to Noncontrolling Interests	(7,519)	(7,519)	(7,519)
Comprehensive Income	986,875	943,864	885,650
The Connecticut Light And Power Company
Net Income	376,726	334,254	299,360
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	334	444	444
Changes in Unrealized (Losses)/Gains on Marketable Securities	(12)	79	(89)
Other Comprehensive (Loss)/Income, Net of Tax	322	523	355
Comprehensive Income	377,048	334,777	299,715
NSTAR Electric Company
Net Income	374,726	350,777	401,048
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	438	437	380
Changes in Unrealized (Losses)/Gains on Marketable Securities	(3)	22	(25)
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	(264)	(177)	103
Other Comprehensive (Loss)/Income, Net of Tax	171	282	458
Comprehensive Income	374,897	351,059	401,506
Public Service Company Of New Hampshire
Net Income	135,996	131,985	114,442
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	1,162	1,162	1,162
Changes in Unrealized (Losses)/Gains on Marketable Securities	(21)	136	(154)
Other Comprehensive (Loss)/Income, Net of Tax	1,141	1,298	1,008
Comprehensive Income	$ 137,137	$ 133,283	$ 115,450