Pensions Benefit Obligation in Excess of Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation	$ 2,072	$ 1,876
Fair value of plan assets	1,557	1,421
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	1,976	1,792
Fair value of plan assets	$ 1,525	$ 1,393