Employment Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Transition period			10 years
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain as a result of plan amendments			$ 120
Service cost	$ 7	$ 12	24	$ 34
Interest cost	20	20	62	62
Expected return on plan assets	(41)	(39)	(120)	(118)
Amortization of net gain	0	0	(1)	0
Amortization of prior service credits	0	0	(3)	0
Curtailment gain	0	0	(117)	0
Net cost recognized	(14)	(7)	(155)	(22)
Retiree Health and Welfare Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1	1
Interest cost	2	2	6	6
Amortization of prior service credits	0	(2)	0	(2)
Net cost recognized	$ 3	$ 1	$ 7	$ 5