FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2018

Maturities for marketable securities (in millions):



September 30, 2018	Cost Basis		Fair Value
Due in one year or less	$	126	$	126
Due after one year through five years	1,094		1,072
Due after five years through 10 years	26		25
Total	$	1,246	$	1,223

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



September 30, 2018	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	338	$	—		$	338
Foreign government bonds	—		29			29
Asset-backed securities	—		209			209
Mortgage-backed securities	—		79			79
Corporate notes and bonds	—		559			559
Municipal securities	—		9			9
Total Marketable securities	338		885			1,223
Derivative instruments
Fuel hedge—call options	—		54			54
Interest rate swap agreements	—		15			15
Total Assets	$	338	$	954		$	1,292

Liabilities
Derivative instruments
Interest rate swap agreements	—		(3		)	(3		)
Total Liabilities	$	—	$	(3	)	$	(3	)



December 31, 2017	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	328	$	—		$	328
Foreign government bonds	—		43			43
Asset-backed securities	—		209			209
Mortgage-backed securities	—		99			99
Corporate notes and bonds	—		726			726
Municipal securities	—		22			22
Total Marketable securities	328		1,099			1,427
Derivative instruments
Fuel hedge—call options	—		22			22
Interest rate swap agreements	—		9			9
Total Assets	$	328	$	1,130		$	1,458

Liabilities
Derivative instruments
Interest rate swap agreements	—		(8		)	(8		)
Total Liabilities	$	—	$	(8	)	$	(8	)

Fixed-rate debt on the consolidated balance sheet and the estimated fair value of long-term fixed-rate debt is as follows (in millions):



	September 30, 2018		December 31, 2017
Fixed-rate debt at cost	$	703	$	956
Non-recurring purchase price accounting fair value adjustment	3		3
Total fixed-rate debt	$	706	$	959

Estimated fair value	$	700	$	959