Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

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, 2018			Level 1			Level 2
Cash equivalents	$	982		$	982		$	—
Short-term investments
U.S. government and agency securities	50			45			5
Asset- and mortgage-backed securities	91			—			91
Corporate obligations	258			—			258
Other fixed income securities	79			—			79
Restricted cash equivalents	1,268			1,268			—
Long-term investments	809			781			28
Hedge derivatives, net
Fuel hedge contracts	(29		)	(19		)	(10		)
Interest rate contracts	(38		)	—			(38		)
Foreign currency exchange contracts	(9		)	—			(9		)

(in millions)	December 31, 2017			Level 1			Level 2
Cash equivalents	$	1,357		$	1,357		$	—
Short-term investments
U.S. government and agency securities	93			84			9
Asset- and mortgage-backed securities	173			—			173
Corporate obligations	467			—			467
Other fixed income securities	92			—			92
Restricted cash equivalents	38			38			—
Long-term investments	513			485			28
Hedge derivatives, net
Fuel hedge contracts	(66		)	(43		)	(23		)
Foreign currency exchange contracts	(17		)	—			(17		)