Special Charges - Components of Special Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Other Income and Expenses [Abstract]
Labor contract ratification bonuses	$ 813	$ 0	$ 813	$ 0
(Gains) losses on sale of assets and other special charges	46	112	60	104
Total operating special charges	859	112	873	104
Nonoperating unrealized (gains) losses on investments, net	(84)	40	(108)	40
Nonoperating debt extinguishment and modification fees	11	0	11	7
Total nonoperating special charges and unrealized (gains) losses on investments, net	(73)	40	(97)	47
Total operating and nonoperating special charges and unrealized (gains) losses on investments, net	786	152	776	151
Income tax benefit, net of valuation allowance	(194)	(10)	(197)	(10)
Total operating and nonoperating special charges and unrealized (gains) losses on investments, net of income taxes	$ 592	$ 142	$ 579	$ 141