Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 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)	March 31, 2016			Level 1			Level 2
Cash equivalents	$	1,137		$	1,137		$	—
Short-term investments
U.S. government and agency securities	160			127			33
Asset- and mortgage-backed securities	238			—			238
Corporate obligations	755			—			755
Other fixed income securities	53			—			53
Restricted cash equivalents and investments	49			49			—
Long-term investments	167			141			26
Hedge derivatives, net
Fuel hedge contracts	(664		)	(101		)	(563		)
Interest rate contract	7			—			7
Foreign currency exchange contracts	(33		)	—			(33		)

(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