CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Tax expense of actuarial gains	$ 10	$ 20	$ 31	$ 77
Tax expense (benefit) of prior service costs	$ 0	$ 1	$ (49)	$ 2