FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2023

Fair Value Disclosures [Abstract]

Investments Classified by Contractual Maturity Date

Maturities for marketable securities (in millions):

March 31, 2023	Cost Basis		Fair Value
Due in one year or less	$	425	$	415
Due after one year through five years	1,532		1,465
Due after five years	28		27
No maturity date	5		6
Total	$	1,990	$	1,913

Fair Value, by Balance Sheet Grouping

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

	March 31, 2023						December 31, 2022
	Level 1		Level 2		Total		Level 1		Level 2		Total
Assets
Marketable securities
U.S. government and agency securities	$	520	$	—	$	520	$	505	$	—	$	505
Equity mutual funds	6		—		6		5		—		5
Foreign government bonds	—		25		25		—		25		25
Asset-backed securities	—		235		235		—		261		261
Mortgage-backed securities	—		160		160		—		196		196
Corporate notes and bonds	—		909		909		—		1,025		1,025
Municipal securities	—		58		58		—		62		62
Total Marketable securities	526		1,387		1,913		510		1,569		2,079
Derivative instruments
Fuel hedge contracts - call options	—		21		21		—		44		44
Interest rate swap agreements	—		12		12		—		15		15
Total Assets	$	526	$	1,420	$	1,946	$	510	$	1,628	$	2,138

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

	March 31, 2023		December 31, 2022
Fixed-rate debt	$	1,591	$	1,660
Estimated fair value	$	1,435	$	1,473