CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement of Comprehensive Income
Reclassification of previously deferred derivative losses to net income, income tax benefit (expense)	$ (5)	$ (9)	$ (12)
Net gain (loss) incurred during period, income tax benefit (expense)	77	52	74
Prior service credit (cost) incurred during period, income tax benefit (expense)	(5)	2
Amortization of net actuarial loss and prior service cost to net periodic benefit cost, income tax benefit (expense)	$ (31)	$ (23)	$ (21)