Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income	$ 989	$ 937	$ 2,671	$ 2,440
Other comprehensive income:
Change in amortization of accumulated actuarial losses and prior service costs, net of tax expense of $2 million, $1 million, $6 million and $3 million, respectively	4	2	10	6
Change in fuel hedge mark-to-market, net of tax benefit of $0 million, $0 million, $0 million and $7 million, respectively	0	0	0	(11)
Change in accumulated other comprehensive income of equity method investees	(1)	0	(2)	(3)
Other comprehensive income (loss), net of tax	3	2	8	(8)
Total comprehensive income	$ 992	$ 939	$ 2,679	$ 2,432