Accumulated Other Comprehensive Loss - Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassifications out of accumulated other comprehensive income loss by component
Interest Expense	$ 449	$ 523
Other income, net	(98)	(5)
Total before tax	433	(6,027)
Income tax expense (benefit)	(119)	(138)
Net income (loss)	314	(6,165)
Decrease (Increase) in Net Income | Interest rate swap
Reclassifications out of accumulated other comprehensive income loss by component
Interest Expense	(5)
Decrease (Increase) in Net Income | Net actuarial loss
Reclassifications out of accumulated other comprehensive income loss by component
Other income, net	50	57
Decrease (Increase) in Net Income | Prior service cost
Reclassifications out of accumulated other comprehensive income loss by component
Other income, net	1	2
Decrease (Increase) in Net Income | Defined benefit plan
Reclassifications out of accumulated other comprehensive income loss by component
Total before tax	56	59
Income tax expense (benefit)	(12)	15
Net income (loss)	$ 44	$ 44