Derivative Instruments and Hedging Activities (Details 1) (Interest expense [Member], USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Gain (Loss) on Swap [Member]
Impact of changes in the fair value of interest rate swaps and the underlying hedged items on results of operations
Impact of changes in the fair value of interest rate swaps and the underlying hedged items on results of operations	$ 18	$ 13	$ 12	$ 14
Gain (Loss) on Fixed-Rate Debt [Member]
Impact of changes in the fair value of interest rate swaps and the underlying hedged items on results of operations
Impact of changes in the fair value of interest rate swaps and the underlying hedged items on results of operations	$ (18)	$ (13)	$ (12)	$ (14)

The amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 205G

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44C
-Subparagraph b

Name:	us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeNet
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration