Operating Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fuel [Line Items]
Fuel Power Costs	$ 516.7	$ 599.4	$ 466.5
Public Service Company Of New Hampshire [Member]
Fuel [Line Items]
Fuel Power Costs	$ 85.4	$ 113.4	$ 104.8