Accumulated Other Comprehensive Loss - Reclassifications (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 1,522	$ 1,668	$ 2,021
Other expense, net	(62)	(76)	(19)
Total before tax	2,701	(782)	(4,766)
Income tax benefit	(668)	(450)	(503)
Net of tax	2,033	(1,232)	$ (5,269)
Decrease (Increase) in Net Income | Interest rate swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	83	62
Income tax benefit	(20)	(16)
Net of tax	63	46
Decrease (Increase) in Net Income | Net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net	190	203
Decrease (Increase) in Net Income | Settlement charge
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net	383
Decrease (Increase) in Net Income | Prior service cost
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net	6	7
Decrease (Increase) in Net Income | Curtailment loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net		4
Decrease (Increase) in Net Income | Defined benefit plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	579	214
Income tax benefit	(142)	(52)
Net of tax	$ 437	$ 162