Derivative Instruments (Textuals) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Maximum length of time hedging using interest rate derivative instruments	9 years
Derivative, Net Liability Position, Aggregate Fair Value	$ 19
Collateral Already Posted, Aggregate Fair Value	11
Additional Collateral, Aggregate Fair Value	5
Other Comprehensive Income Loss Derivatives Qualifying As Hedges Tax	0	3	11
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	0	0	(2)
(Gain) Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	10	12
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	(46)
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	0	0	(14)
Gain Loss On Interest Rate Derivative Instruments Not Designated As Hedging Instruments, Unrealized			14
Gain Loss On Interest Rate Derivative Instruments Not Designated As Hedging Instruments, Realized			142
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments			156
Parent [Member]
Derivatives, Fair Value [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(149)	(148)	(222)
Noncontrolling Interest [Member]
Derivatives, Fair Value [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	$ (12)	$ (11)	$ (20)