Equity (Comprehensive Income Equity) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Equity [Abstract]
Net income	$ 203		$ 261		$ 771		$ 859
Employee benefit plan adjustment, net of tax	8	[1]	8	[1]	26	[1]	(64)	[1]
Comprehensive income	211		269		797		795
Tax (expense) benefit from employee benefit plans	$ 6		$ 7		$ 17		$ 42

[1] These balances are net of income tax expense of $6 million and $7 million for the three months ended September 30, 2011 and 2010, respectively. For the nine months ended September 30, 2011 and 2010, the income tax expense was $17 million and the income tax benefit was $42 million, respectively.