Employee Benefit Plans - Net Periodic Cost and OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Rate of compensation increase
Health care trend rate (as a percent)	5.80%	4.90%
Ultimate health care trend rate (as a percent)	4.53%
Defined Benefit Plans
Amounts recognized in net periodic benefit cost and other comprehensive income (loss)
Current year actuarial gain (loss)	$ 21	$ 45	$ (24)
Amortization of actuarial loss	(14)	(15)	(16)
Current year prior service cost	0	5	0
Amortization of prior service cost	(1)	(3)	(1)
Curtailments	9	(23)	4
Other	0	0	(3)
Total recognized in other comprehensive loss	15	9	(40)
Net periodic benefit cost	(9)	24	0
Total recognized in net periodic benefit cost and other comprehensive loss	$ 6	$ 33	$ (40)
Projected benefit obligation:
Discount rate	1.60%	2.38%	2.21%
Rate of compensation increase	2.56%	3.69%	3.74%
Rate of compensation increase
Discount rate	2.38%	2.21%	1.86%
Rate of compensation increase	3.69%	3.74%	3.53%
Expected return on plan assets	5.23%	5.23%	5.71%
Other Postretirement Benefit Plans
Amounts recognized in net periodic benefit cost and other comprehensive income (loss)
Current year actuarial gain (loss)	$ 1	$ 0	$ (1)
Amortization of actuarial loss	0	0	(1)
Amortization of prior service cost	0	0	3
Total recognized in other comprehensive loss	2	0	1
Net periodic benefit cost	(1)	0	(2)
Total recognized in net periodic benefit cost and other comprehensive loss	$ 1	$ 0	$ (1)
Projected benefit obligation:
Discount rate	3.27%	3.50%	3.38%
Rate of compensation increase
Discount rate	3.51%	3.30%	3.72%
Rate of compensation increase	4.35%	0.00%	0.00%