Income Taxes - Valuation Allowances Against Deferred Tax Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Valuation Allowances Against Deferred Tax Assets
Settlement of tax matters with Former Parent1	$ 0	$ (101)
Held for sale	(47)	0
Deferred tax asset valuation allowance
Valuation Allowances Against Deferred Tax Assets
Allowances at beginning of year	125	150
Allowances at end of year	179	125
Deferred tax asset valuation allowance | Benefits reserved current year
Valuation Allowances Against Deferred Tax Assets
Benefits reserved current year	102	83
Deferred tax asset valuation allowance | Change in Tax rate /impact of U.S. tax reform
Valuation Allowances Against Deferred Tax Assets
Change in Tax rate /impact of U.S. tax reform	0	(4)
Deferred tax asset valuation allowance | Translation difference
Valuation Allowances Against Deferred Tax Assets
Translation difference	$ (1)	$ (3)