Pension and Other Postretirement Benefits - Schedule of Weighted Average Assumptions Used to Determine Benefit Obligations (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate		4.35%	3.75%
Rate of compensation increase		3.50%	3.50%
Cash balance plan interest crediting rate		3.00%	3.00%
Average duration for plans' projected cash flows		10 years
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate to calculate service cost		3.75%	4.20%	4.29%
Discount rate to calculate interest cost		3.30%	3.60%	3.15%
Expected long-term rate of return on plan assets		7.00%	7.75%	7.75%
Rate of compensation increase		3.50%	3.50%	3.50%
Cash balance plan interest crediting rate		0.0300	0.0300	0.0300
Period expected long-term rate of return is applied		5 years
Number of years over actual annual healthcare cost trend experience		20 years
Basis point of decrease identified In long term rate of return		0.75%
Pension benefits paid
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Period of observation to determine average compensation increase		5 years
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Interest cost component related to net periodic benefit cost		$ 24	$ 34	$ 84
Other postretirement benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Interest cost component related to net periodic benefit cost		$ 4	$ 6	$ 14
Number of years over actual annual healthcare cost trend experience		3 years
Scenario, Forecast
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Expected long-term rate of return on plan assets	7.00%