FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Investments Classified by Contractual Maturity Date

Maturities for marketable securities (in millions):

September 30, 2023	Cost Basis		Fair Value
Due in one year or less	$	403	$	395
Due after one year through five years	1,386		1,320
Due after five years	73		68
Due after 10 years	18		16
No maturity date	4		5
Total	$	1,884	$	1,804

Fair Value, by Balance Sheet Grouping

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

	September 30, 2023						December 31, 2022
	Level 1		Level 2		Total		Level 1		Level 2		Total
Assets
Marketable securities
U.S. government and agency securities	$	508	$	—	$	508	$	505	$	—	$	505
Equity mutual funds	5		—		5		5		—		5
Foreign government bonds	—		10		10		—		25		25
Asset-backed securities	—		216		216		—		261		261
Mortgage-backed securities	—		123		123		—		196		196
Corporate notes and bonds	—		889		889		—		1,025		1,025
Municipal securities	—		53		53		—		62		62
Total Marketable securities	513		1,291		1,804		510		1,569		2,079
Derivative instruments
Fuel hedge contracts - call options	—		40		40		—		44		44
Interest rate swap agreements	—		13		13		—		15		15
Total Assets	$	513	$	1,344	$	1,857	$	510	$	1,628	$	2,138

Fixed-rate debt on the condensed consolidated balance sheets and the estimated fair value of long-term fixed-rate debt (in millions):

	September 30, 2023		December 31, 2022
Fixed-rate debt	$	1,520	$	1,660
Estimated fair value	$	1,372	$	1,473