FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value, Measurement Inputs, Disclosure

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

March 31, 2017	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	416	$	—		$	416
Foreign government bonds	—		38			38
Asset-backed securities	—		194			194
Mortgage-backed securities	—		88			88
Corporate notes and bonds	—		780			780
Municipal securities	—		11			11
Total Marketable securities	416		1,111			1,527
Derivative instruments
Fuel hedge call options	—		10			10
Interest rate swap agreements	—		9			9
Total Assets	416		1,130			1,546
Liabilities
Derivative instruments
Interest rate swap agreements	—		(12		)	(12		)
Total Liabilities	—		(12		)	(12		)

December 31, 2016	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	287	$	—		$	287
Foreign government bonds	—		36			36
Asset-backed securities	—		138			138
Mortgage-backed securities	—		89			89
Corporate notes and bonds	—		691			691
Municipal securities	—		11			11
Total Marketable securities	287		965			1,252
Derivative instruments
Fuel hedge call options	—		20			20
Total Assets	287		985			1,272
Liabilities
Derivative instruments
Interest rate swap agreements	—		(5		)	(5		)
Total Liabilities	—		(5		)	(5		)

Activity for Marketable Securities

Activity for marketable securities (in millions):  

	Three Months Ended March 31,
	2017			2016
Proceeds from sales and maturities	$	285		$	140
Gross realized gains	1			—
Gross realized losses	(1		)	—
Gross unrealized gains	3			10
Gross unrealized losses	(5		)	(2		)

Schedule of Marketable Security Maturities

Maturities for marketable securities (in millions):

March 31, 2017	Cost Basis		Fair Value
Due in one year or less	$	236	$	236
Due after one year through five years	1,281		1,278
Due after five years through 10 years	12		13
Due after 10 years	—		—
Total	$	1,529	$	1,527

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 is as follows (in millions):

	March 31, 2017		December 31, 2016
Carrying amount	$	1,116	$	1,179
Fair value	1,130		1,199