Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Schedule of assets (liabilities) measured at fair value on a recurring basis

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

(in millions)	September 30, 2017			Level 1			Level 2
Cash equivalents	$	169		$	169		$	—
Short-term investments
U.S. government and agency securities	152			142			10
Asset- and mortgage-backed securities	188			—			188
Corporate obligations	519			—			519
Other fixed income securities	101			—			101
Restricted cash equivalents and investments	39			39			—
Long-term investments	399			371			28
Hedge derivatives, net
Fuel hedge contracts	(139		)	(31		)	(108		)
Interest rate contract	(4		)	—			(4		)
Foreign currency exchange contracts	(22		)	—			(22		)

(in millions)	December 31, 2016			Level 1			Level 2
Cash equivalents	$	2,279		$	2,279		$	—
Short-term investments
U.S. government and agency securities	112			86			26
Asset- and mortgage-backed securities	68			—			68
Corporate obligations	295			—			295
Other fixed income securities	12			—			12
Restricted cash equivalents and investments	61			61			—
Long-term investments	139			115			24
Hedge derivatives, net
Fuel hedge contracts	(324		)	(26		)	(298		)
Interest rate contract	6			—			6
Foreign currency exchange contracts	27			—			27