Employment Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Number of months for highest consecutive compensation				60 months
Total number of years of salaried employees to qualify for pension plans				10 years
Transition period				10 years
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain as a result of plan amendments			$ 120
Curtailment gain	$ 0	$ 0	(117)	$ 0	$ (117)
Amortization of prior service credits	0	0	$ (3)	0	(3)
Service cost	6	7		16	24
Interest cost	18	20		53	62
Expected return on plan assets	(42)	(41)		(126)	(120)
Amortization of net gain	0	0		1	(1)
Net cost recognized	$ (18)	$ (14)		$ (56)	$ (155)