Fair Value Measurement - Quantitative Information - Assets (Details) - Valuation, Income Approach [Member] - Level 3 [Member] - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Obligations of state and political subdivisions [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 97	$ 107
Obligations of state and political subdivisions [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	5.30%	4.50%
Obligations of state and political subdivisions [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	35.30%	31.10%
Obligations of state and political subdivisions [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	10.90%	8.50%
Corporate securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 29	$ 41
Yield (as a percent)	45.30%	35.90%
RMBS [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 254	$ 308
RMBS [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	4.50%	3.70%
RMBS [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	7.20%	6.10%
RMBS [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	5.50%	4.80%
Life Insurance Transaction [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 335	$ 350
Yield (as a percent)	5.50%
Life Insurance Transaction [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)		5.80%
Collateralized loan obligations (CLO) /TruPS [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 342	$ 256
Collateralized loan obligations (CLO) /TruPS [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	1.50%	2.50%
Collateralized loan obligations (CLO) /TruPS [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	4.20%	4.10%
Collateralized loan obligations (CLO) /TruPS [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	2.40%	2.90%
Other Asset Backed Securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 37	$ 52
Yield (as a percent)	13.30%
Other Asset Backed Securities [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)		2.30%
Other Asset Backed Securities [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)		9.40%
Other Asset Backed Securities [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)		9.30%
FG VIEs and other [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 318	$ 442
FG VIEs and other [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	2.90%	3.00%
FG VIEs and other [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	8.70%	8.40%
FG VIEs and other [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	5.90%	5.20%
Other Assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 75	$ 52
Fair Value Inputs Term	10 years	10 years
Other Assets [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	4.00%	5.10%
Other Assets [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	4.80%	5.80%
Other Assets [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	4.40%	5.50%
Other invested assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 6	$ 6
Measurement Input, Prepayment Rate [Member] | RMBS [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	2.70%	2.00%
Measurement Input, Prepayment Rate [Member] | RMBS [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	15.00%	15.00%
Measurement Input, Prepayment Rate [Member] | RMBS [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	6.50%	6.30%
Measurement Input, Prepayment Rate [Member] | FG VIEs and other [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	0.40%	0.10%
Measurement Input, Prepayment Rate [Member] | FG VIEs and other [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	18.80%	18.60%
Measurement Input, Prepayment Rate [Member] | FG VIEs and other [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	8.60%	8.60%
Measurement Input, Default Rate [Member] | RMBS [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	1.50%	1.50%
Measurement Input, Default Rate [Member] | RMBS [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	7.50%	7.00%
Measurement Input, Default Rate [Member] | RMBS [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	5.40%	4.90%
Measurement Input, Default Rate [Member] | FG VIEs and other [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	1.20%	1.20%
Measurement Input, Default Rate [Member] | FG VIEs and other [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	26.50%	24.70%
Measurement Input, Default Rate [Member] | FG VIEs and other [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	5.30%	4.90%
Measurement Input, Loss Severity [Member] | RMBS [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	45.00%	40.00%
Measurement Input, Loss Severity [Member] | RMBS [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	125.00%	125.00%
Measurement Input, Loss Severity [Member] | RMBS [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	83.40%	78.80%
Measurement Input, Loss Severity [Member] | FG VIEs and other [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	45.00%	40.00%
Measurement Input, Loss Severity [Member] | FG VIEs and other [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	100.00%	100.00%
Measurement Input, Loss Severity [Member] | FG VIEs and other [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed	79.70%	76.10%
Measurement Input, Discount Rate [Member] | Structured Products [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	11.60%
Assets of Consolidated Investment Vehicles [Member] | Debt Securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 60
Assets of Consolidated Investment Vehicles [Member] | Debt Securities [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	14.90%
Assets of Consolidated Investment Vehicles [Member] | Debt Securities [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	23.40%
Assets of Consolidated Investment Vehicles [Member] | Debt Securities [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	18.50%
Assets of Consolidated Investment Vehicles [Member] | Equity Securities and Warrants [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 53	$ 17
Yield (as a percent)	10.10%	12.50%
Assets of Consolidated Investment Vehicles [Member] | Structured Products [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value	$ 6
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Debt Securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets carried at fair value		$ 47
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Debt Securities [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed		16.00%
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Debt Securities [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed		28.00%
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Debt Securities [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Transferor's continuing involvement, servicing assets or liabilities, prepayment speed		21.50%
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Equity Securities and Warrants [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	14.90%	16.00%
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Equity Securities and Warrants [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	26.90%	28.00%
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Equity Securities and Warrants [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	25.60%	20.80%
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Structured Products [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	4.80%
Assets of Consolidated Investment Vehicles [Member] | Measurement Input, Discount Rate [Member] | Structured Products [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	7.40%