Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jan. 01, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, Current Period, Tax	$ (7)	$ (3)	$ (7)	$ (7)
Adjustment of retained earnings	2,015		2,015		$ 1,792
Accounting Standards Update 2018-02 [Member] | Defined pension and post-retirement benefit costs [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Adjustment of retained earnings	$ 0	$ (36)	$ 0	$ (36)		$ 36