Fair Value Measurements - Significant Unobservable Inputs - Derivatives (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Equity options
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative Assets (Liabilities), at Fair Value, Net	$ (15)	$ 3
Interest Rate Swaption
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative Assets (Liabilities), at Fair Value, Net		$ 1
Interest Rate Swaption | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve		3.00%
Interest Rate Swaption | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve		3.00%
Interest Rate Swaption | Weighted Average Expected Life
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve		3.00%
Measurement Input, Option Volatility [Member] | Equity options | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve	13.00%	19.00%
Measurement Input, Option Volatility [Member] | Equity options | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve	28.00%	21.00%
Measurement Input, Option Volatility [Member] | Equity options | Weighted Average Expected Life
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve	17.00%	20.00%