Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013 MWh MMBTU	Dec. 31, 2012 MWh MMBTU
Derivative Instruments [Abstract]
Power (MWh)	(29)	(16)
Natural gas (MMBtu)	448	66
Interest rate swaps	$ 1,527	$ 1,602

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant