Legal Proceedings Loss Contingencies (Details) (Pending Litigation [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Pending Litigation [Member]
Loss Contingencies [Line Items]
Approximate amount of refunds received as a net purchaser of power through settlements with sellers of power	$ 8
Estimated additional refunds entitled to receive	$ 12

Amount of judgment or settlement awarded to (against) the entity in respect of litigation.

No definition available.

Name:	us-gaap_LitigationSettlementAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration