FAIR VALUE MEASUREMENTS (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Activity for Marketable Securities

Investments Classified by Contractual Maturity Date

Maturities for marketable securities (in millions):

June 30, 2019	Cost Basis		Fair Value
Due in one year or less	$	298	$	299
Due after one year through five years	1,065		1,080
Due after five years through 10 years	4		4
Total	$	1,367	$	1,383

Fair Value, by Balance Sheet Grouping

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, 2019		December 31, 2018
Fixed-rate debt at cost	$	580	$	639
Non-recurring purchase price accounting fair value adjustment	2		3
Total fixed-rate debt	$	582	$	642
Estimated fair value	$	595	$	641

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

	June 30, 2019								December 31, 2018
	Level 1		Level 2			Total			Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	409	$	—		$	409		$	293	$	—		$	293
Foreign government bonds	—		25			25			—		26			26
Asset-backed securities	—		189			189			—		190			190
Mortgage-backed securities	—		120			120			—		92			92
Corporate notes and bonds	—		623			623			—		520			520
Municipal securities	—		17			17			—		10			10
Total Marketable securities	409		974			1,383			293		838			1,131
Derivative instruments
Fuel hedge—call options	—		7			7			—		4			4
Interest rate swap agreements	—		4			4			—		10			10
Total Assets	$	409	$	985		$	1,394		$	293	$	852		$	1,145
Liabilities
Derivative instruments
Interest rate swap agreements	—		(10		)	(10		)	—		(7		)	(7		)
Total Liabilities	$	—	$	(10	)	$	(10	)	$	—	$	(7	)	$	(7	)