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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 49		$ 49
Unfunded Commitments	13		13
Funded Commitments	0	$ 1	4	$ 1
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	48		48
Unfunded Commitments	13		13
Funded Commitments	0	1	4	1
Funded Other	$ 0	$ 0	$ 0	$ 0