FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping [Table Text Block]

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

	December 31, 2021						December 31, 2020
	Level 1		Level 2		Total		Level 1		Level 2		Total
Assets
Marketable securities
U.S. government and agency securities	$	331	$	—	$	331	$	407	$	—	$	407
Equity mutual funds	6		—		6		7		—		7
Foreign government bonds	—		38		38		—		20		20
Asset-backed securities	—		311		311		—		224		224
Mortgage-backed securities	—		232		232		—		290		290
Corporate notes and bonds	—		1,663		1,663		—		978		978
Municipal securities	—		65		65		—		50		50
Total Marketable securities	337		2,309		2,646		414		1,562		1,976
Derivative instruments
Fuel hedge contracts - call options	—		81		81		—		15		15
Total Assets	$	337	$	2,390	$	2,727	$	414	$	1,577	$	1,991
Liabilities
Derivative instruments
Interest rate swap agreements	—		(9)		(9)		—		(25)		(25)
Total Liabilities	$	—	$	(9)	$	(9)	$	—	$	(25)	$	(25)

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

	December 31, 2021		December 31, 2020
Total fixed rate debt	$	1,821	$	1,662
Estimated fair value	$	1,919	$	1,778

Schedule of Realized Gain (Loss) [Table Text Block]

Proceeds from sales of marketable securities were $3.6 billion, $2.3 billion and $1.7 billion in 2021, 2020, and 2019.

Schedule of Debt Investment Maturities [Table Text Block]

Maturities for marketable securities (in millions):

December 31, 2021	Cost Basis		Fair Value
Due in one year or less	$	1,064	$	1,065
Due after one year through five years	1,537		1,532
Due after five years	44		42
Total	$	2,645	$	2,639