Income Taxes - Valuation Allowances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation Allowance [Line Items]
Valuation allowance, deferred tax assets	$ 0	$ 0
Tax valuation allowance allocated to Net income (loss)
Valuation Allowance [Line Items]
Valuation allowance, deferred tax assets	128	128
Increase (decrease) in valuation allowance	0	9	$ (5)
Deferred Tax Asset, Capital Loss Carryforward
Valuation Allowance [Line Items]
Valuation allowance, deferred tax assets	128	128
Increase (decrease) in valuation allowance	$ 0	$ 9	$ 0