ACCOUNTING STANDARDS (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Liabilities Current		$ 160,288
Available for sale securities subject to new accounting guidance	$ 52,000
The Connecticut Light And Power Company [Member]
Deferred Tax Liabilities Current		34,100
NSTAR Electric Company [Member]
Deferred Tax Liabilities Current	0	55,136
Public Service Company Of New Hampshire [Member]
Deferred Tax Liabilities Current	0	36,164
Western Massachusetts Electric Company [Member]
Deferred Tax Liabilities Current	$ 0	$ 18,089