Derivative Instruments and Hedging Activities (Commodity Derivatives) (Details) - Power MWh - Commodity Contract [Member] MWh in Millions	12 Months Ended
	Dec. 31, 2015 MWh
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	10
Derivative average remaining maturity	3 years	[1]

[1] (1) Represents the remaining tenor of our commodity derivatives weighted by the corresponding volume. These derivatives range in maturity through 2018.