Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 802	$ 690	$ 1,503	$ 1,297
Other comprehensive income:
Change in amortization of accumulated actuarial losses, net of tax expense of $0 million, $0 million, $2 million and $0 million, respectively	2	0	4	0
Change in fuel hedge mark-to-market, net of tax benefit of $2 million, $26 million, $7 million and $1 million, respectively	(3)	(41)	(11)	(1)
Change in other comprehensive income of equity method investees	(1)	(1)	(3)	0
Other comprehensive loss, net of tax	(2)	(42)	(10)	(1)
Total comprehensive income	$ 800	$ 648	$ 1,493	$ 1,296