Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income	$ 798	$ 701
Other comprehensive income:
Change in amortization of accumulated actuarial losses, net of tax expense of $2 million and $2 million, respectively	3	2
Change in fuel hedge mark-to-market, net of tax benefit of $0 million and $4 million, respectively	0	(8)
Change in accumulated other comprehensive income of equity method investees	(2)	(2)
Other comprehensive income (loss), net of tax	1	(8)
Total comprehensive income	$ 799	$ 693