Fair Value Measurements - Fair Value of Direct and Indirect Investments, Related Unfunded Commitments and Financial Support Provided (Details) - Principal Investments - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 61		$ 61
Unfunded Commitments	18		18
Funded Commitments	1	$ 0	1	$ 2
Funded Other	0	0	0	0
Direct investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	1		1
Unfunded Commitments	0		0
Funded Commitments	0	0	0	0
Funded Other	0	0	0	0
Indirect investments (measured at NAV)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	60		60
Unfunded Commitments	18		18
Funded Commitments	1	0	1	2
Funded Other	$ 0	$ 0	$ 0	$ 0