Employee Benefit Plans - Change in Level 3 Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	$ 107	$ 116
Fair value of assets at end of year	129	107
Level 3
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	4	4
Unrealized gain (loss) on asset still held	1	0
Fair value of assets at end of year	$ 5	$ 4