Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Disclosures [Abstract]

Assets (liabilities) measured at fair value on a recurring basis

Assets (Liabilities) Measured at Fair Value on a Recurring Basis

(in millions)	June 30, 2016			Level 1		Level 2
Cash equivalents	$	1,058		$	1,058	$	—
Short-term investments
U.S. government and agency securities	191			167		24
Asset- and mortgage-backed securities	252			—		252
Corporate obligations	785			—		785
Other fixed income securities	61			—		61
Restricted cash equivalents and investments	62			62		—
Long-term investments	154			128		26
Hedge derivatives, net
Fuel hedge contracts	(239		)	11		(250		)
Interest rate contract	11			—		11
Foreign currency exchange contracts	(79		)	—		(79		)

(in millions)	December 31, 2015			Level 1		Level 2
Cash equivalents	$	1,543		$	1,543	$	—
Short-term investments
U.S. government and agency securities	151			74		77
Asset- and mortgage-backed securities	380			—		380
Corporate obligations	896			—		896
Other fixed income securities	38			—		38
Restricted cash equivalents and investments	49			49		—
Long-term investments	155			130		25
Hedge derivatives, net
Fuel hedge contracts	(672		)	65		(737		)
Interest rate contract	(3		)	—		(3		)
Foreign currency exchange contracts	94			—		94