Consolidated Statement of Stockholder's Equity (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stockholders' equity	$ 6,992	$ 6,877	$ 6,237	$ 5,454
Purchase of shares of treasury stock	(400)	(225)
Issuance of common and treasury stock pursuant to Employee stock plans	23	20	54
Issuance of stock to acquire AirTran		523
Issuance of stock for conversion debt		112
Net tax benefit (expense) of options excercised	(24)	(5)	(45)
Share-based compensation	16	13	12
Cash dividends	(26)	(14)	(13)
Comprehensive income (loss) [Abstract]
Comprehensive income (loss)	526	216	775
Common Stock [Member]
Stockholders' equity	808	808	808	808
Purchase of shares of treasury stock	0	0
Issuance of common and treasury stock pursuant to Employee stock plans	0	0	0
Issuance of stock to acquire AirTran		0
Issuance of stock for conversion debt		0
Net tax benefit (expense) of options excercised	0	0	0
Share-based compensation	0	0	0
Cash dividends	0	0	0
Comprehensive income (loss) [Abstract]
Comprehensive income (loss)	0	0	0
Additional Paid-in Capital [Member]
Stockholders' equity	1,210	1,222	1,183	1,216
Purchase of shares of treasury stock	0	0
Issuance of common and treasury stock pursuant to Employee stock plans	(4)	(3)	0
Issuance of stock to acquire AirTran		0
Issuance of stock for conversion debt		34
Net tax benefit (expense) of options excercised	(24)	(5)	(45)
Share-based compensation	16	13	12
Cash dividends	0	0	0
Comprehensive income (loss) [Abstract]
Comprehensive income (loss)	0	0	0
Retained Earnings [Member]
Stockholders' equity	5,768	5,395	5,399	4,971
Purchase of shares of treasury stock	0	0
Issuance of common and treasury stock pursuant to Employee stock plans	(22)	(14)	(18)
Issuance of stock to acquire AirTran		(127)
Issuance of stock for conversion debt		(27)
Net tax benefit (expense) of options excercised	0	0	0
Share-based compensation	0	0	0
Cash dividends	(26)	(14)	(13)
Comprehensive income (loss) [Abstract]
Comprehensive income (loss)	421	178	459
Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' equity	(119)	(224)	(262)	(578)
Purchase of shares of treasury stock	0	0
Issuance of common and treasury stock pursuant to Employee stock plans	0	0	0
Issuance of stock to acquire AirTran		0
Issuance of stock for conversion debt		0
Net tax benefit (expense) of options excercised	0	0	0
Share-based compensation	0	0	0
Cash dividends	0	0	0
Comprehensive income (loss) [Abstract]
Comprehensive income (loss)	105	38	316
Treasury Stock [Member]
Stockholders' equity	(675)	(324)	(891)	(963)
Purchase of shares of treasury stock	(400)	(225)
Issuance of common and treasury stock pursuant to Employee stock plans	49	37	72
Issuance of stock to acquire AirTran		650
Issuance of stock for conversion debt		105
Net tax benefit (expense) of options excercised	0	0	0
Share-based compensation	0	0	0
Cash dividends	0	0	0
Comprehensive income (loss) [Abstract]
Comprehensive income (loss)	$ 0	$ 0	$ 0