Commitments and Contingencies, Variable Interest Entities (Details) - MW	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Purchased Power Agreements (PPAs) [Abstract]
VIE Purchase Power Agreement Expiration (year)	2032
Independent Power Producing Entities
Purchased Power Agreements (PPAs) [Abstract]
Generating capacity (in MW)	1,802	1,802