CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Comprehensive Income [Abstract]
Reclassification of previously deferred derivative losses to net income, tax effect	$ (4)	$ (5)	$ (9)
Net gain (loss) incurred during period, tax effect	56	77	52
Prior service credit (cost) incurred during period, tax effect		(5)	2
Amortization of net actuarial loss and prior service cost to net periodic benefit cost, tax effect	$ (32)	$ (31)	$ (23)