Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2019

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)	June 30, 2019			Level 1			Level 2
Cash equivalents	$	1,648		$	1,648		$	—
Restricted cash equivalents	1,020			1,020			—
Long-term investments	1,185			980			205
Hedge derivatives, net
Fuel hedge contracts	(4		)	(18		)	14
Interest rate contracts	62			—			62
Foreign currency exchange contracts	3			—			3

(in millions)	December 31, 2018			Level 1		Level 2
Cash equivalents	$	1,222		$	1,222	$	—
Restricted cash equivalents	1,183			1,183		—
Short-term investments
U.S. government and agency securities	50			45		5
Asset- and mortgage-backed securities	36			—		36
Corporate obligations	90			—		90
Other fixed income securities	27			—		27
Long-term investments	1,084			880		204
Hedge derivatives, net
Fuel hedge contracts	15			20		(5		)
Interest rate contracts	1			—		1
Foreign currency exchange contracts	(3		)	—		(3		)