FAIR VALUE MEASUREMENTS (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Disclosures [Abstract]

Fair Value, Measurement Inputs, Disclosure

Fair values of financial instruments on the consolidated balance sheet (in millions):

June 30, 2016	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	433	$	—		$	433
Foreign government bonds	—		32			32
Asset-backed securities	—		161			161
Mortgage-backed securities	—		113			113
Corporate notes and bonds	—		770			770
Municipal securities	—		17			17
Total Marketable securities	433		1,093			1,526
Derivative instruments
Fuel hedge call options	—		19			19
Total Assets	433		1,112			1,545
Liabilities
Derivative instruments
Interest rate swap agreements	—		(22		)	(22		)
Total Liabilities	—		(22		)	(22		)

December 31, 2015	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	253	$	—		$	253
Foreign government bonds	—		31			31
Asset-backed securities	—		130			130
Mortgage-backed securities	—		116			116
Corporate notes and bonds	—		708			708
Municipal securities	—		17			17
Total Marketable securities	253		1,002			1,255
Derivative instruments
Fuel hedge call options	—		4			4
Total Assets	253		1,006			1,259
Liabilities
Derivative instruments
Interest rate swap agreements	—		(18		)	(18		)
Total Liabilities	—		(18		)	(18		)

Fair Value, by Balance Sheet Grouping

Fixed-rate debt that is not carried at fair value on the consolidated balance sheet and the estimated fair value of long-term fixed-rate debt (in millions) is as follows:

	June 30, 2016		December 31, 2015
Carrying amount	$	474	$	520
Fair value	509		557