Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

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⁽¹⁾ 

(in millions)	December 31, 2014			Level 1			Level 2			Valuation Technique
Cash equivalents	$	1,612		$	1,612		$	—		(a)
Short-term investments
U.S. government and agency securities	59			—			59			(a)
Asset- and mortgage-backed securities	392			—			392			(a)
Corporate obligations	749			—			749			(a)
Other fixed income securities	17			—			17			(a)
Restricted cash equivalents and investments	37			37			—			(a)
Long-term investments	118			90			28			(a)(b)
Hedge derivatives, net
Fuel hedge contracts	(1,848		)	(167		)	(1,681		)	(a)(b)
Interest rate contracts	(7		)	—			(7		)	(a)(b)
Foreign currency exchange contracts	73			—			73			(a)

(in millions)	December 31, 2013			Level 1		Level 2			Valuation Technique
Cash equivalents	$	2,487		$	2,487	$	—		(a)
Short-term investments
U.S. government securities	959			959		—			(a)
Restricted cash equivalents and investments	118			118		—			(a)
Long-term investments	109			80		29			(a)(b)
Hedge derivatives, net
Fuel hedge contracts	314			16		298			(a)(b)
Interest rate contracts	(67		)	—		(67		)	(a)(b)
Foreign currency exchange contracts	257			—		257			(a)

⁽¹⁾  See Note 11, “Employee Benefit Plans,” for fair value of benefit plan assets.