REGULATORY ACCOUNTING (Tables)

12 Months Ended

Dec. 31, 2016

Regulated Operations [Abstract]

Schedule of Regulatory Assets

The components of regulatory assets were as follows:

Eversource (Millions of Dollars)	As of December 31,
	2016		2015
Benefit Costs	$	1,817.8	$	1,828.2
Derivative Liabilities	423.3		388.0
Income Taxes, Net	644.5		650.9
Storm Restoration Costs	385.3		436.9
Goodwill-related	464.4		484.9
Regulatory Tracker Mechanisms	576.6		526.5
Contractual Obligations - Yankee Companies	84.9		134.4
Other Regulatory Assets	129.5		134.0
Total Regulatory Assets	4,526.3		4,583.8
Less:  Current Portion	887.6		845.8
Total Long-Term Regulatory Assets	$	3,638.7	$	3,738.0

	As of December 31,
	2016								2015
(Millions of Dollars)	CL&P		NSTAR Electric		PSNH		WMECO		CL&P		NSTAR Electric		PSNH		WMECO
Benefit Costs	$	429.3	$	438.6	$	184.2	$	86.7	$	413.6	$	479.9	$	164.2	$	84.9
Derivative Liabilities	420.5		2.8		—		—		380.8		1.3		—		—
Income Taxes, Net	437.0		89.7		24.2		30.8		444.4		85.7		34.5		31.8
Storm Restoration Costs	239.8		112.5		17.1		15.9		271.4		110.9		31.5		23.1
Goodwill-related	—		398.7		—		—		—		416.3		—		—
Regulatory Tracker Mechanisms	123.9		257.3		104.5		46.7		45.1		311.0		101.2		40.1
Other Regulatory Assets	76.6		47.5		32.7		11.3		82.0		56.3		31.5		11.3
Total Regulatory Assets	1,727.1		1,347.1		362.7		191.4		1,637.3		1,461.4		362.9		191.2
Less:  Current Portion	335.5		289.4		117.2		64.1		268.3		348.4		105.0		56.2
Total Long-Term Regulatory Assets	$	1,391.6	$	1,057.7	$	245.5	$	127.3	$	1,369.0	$	1,113.0	$	257.9	$	135.0

Schedule of Regulatory Liabilities

The components of regulatory liabilities were as follows:

Eversource (Millions of Dollars)	As of December 31,
	2016		2015
Cost of Removal	$	459.7	$	437.1
Regulatory Tracker Mechanisms	145.3		99.7
Benefit Costs	136.2		—
AFUDC - Transmission	65.8		66.1
Other Regulatory Liabilities	42.1		18.5
Total Regulatory Liabilities	849.1		621.4
Less:  Current Portion	146.8		107.8
Total Long-Term Regulatory Liabilities	$	702.3	$	513.6

	As of December 31,
	2016								2015
(Millions of Dollars)	CL&P		NSTAR Electric		PSNH		WMECO		CL&P		NSTAR Electric		PSNH		WMECO
Cost of Removal	$	38.8	$	271.6	$	44.1	$	8.6	$	24.1	$	257.4	$	47.2	$	2.8
Benefit Costs	—		113.1		—		—		—		—		—		—
Regulatory Tracker Mechanisms	37.2		63.7		10.7		14.7		56.2		3.3		3.4		12.9
AFUDC - Transmission	50.2		6.9		—		8.7		51.5		5.7		—		8.9
Other Regulatory Liabilities	21.0		0.2		2.7		0.1		4.2		1.3		4.2		0.1
Total Regulatory Liabilities	147.2		455.5		57.5		32.1		136.0		267.7		54.8		24.7
Less:  Current Portion	47.1		63.7		12.7		14.9		61.2		3.3		6.9		13.1
Total Long-Term Regulatory Liabilities	$	100.1	$	391.8	$	44.8	$	17.2	$	74.8	$	264.4	$	47.9	$	11.6