FAIR VALUE MEASUREMENTS (Tables)

6 Months Ended

Jun. 30, 2018

Maturities for marketable securities (in millions):



June 30, 2018	Cost Basis		Fair Value
Due in one year or less	$	263	$	262
Due after one year through five years	1,195		1,173
Due after five years through 10 years	31		31
Total	$	1,489	$	1,466

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



	June 30, 2018		December 31, 2017
Fixed-rate debt at cost	$	838	$	956
Non-recurring purchase price accounting fair value adjustment	3		3
Total fixed-rate debt	$	841	$	959

Estimated fair value	$	831	$	959

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



June 30, 2018	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	376	$	—		$	376
Foreign government bonds	—		28			28
Asset-backed securities	—		231			231
Mortgage-backed securities	—		78			78
Corporate notes and bonds	—		743			743
Municipal securities	—		10			10
Total Marketable securities	376		1,090			1,466
Derivative instruments
Fuel hedge—call options	—		58			58
Interest rate swap agreements	—		14			14
Total Assets	$	376	$	1,162		$	1,538

Liabilities
Derivative instruments
Interest rate swap agreements	—		(4		)	(4		)
Total Liabilities	$	—	$	(4	)	$	(4	)



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	)