Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2017

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, 2017			Level 1			Level 2
Cash equivalents	$	1,720		$	1,720		$	—
Short-term investments
U.S. government and agency securities	103			96			7
Asset- and mortgage-backed securities	158			—			158
Corporate obligations	405			—			405
Other fixed income securities	81			—			81
Restricted cash equivalents and investments	63			63			—
Long-term investments	133			107			26
Hedge derivatives, net
Fuel hedge contracts	(203		)	(52		)	(151		)
Interest rate contract	(4		)	—			(4		)
Foreign currency exchange contracts	(7		)	—			(7		)

(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