Other assets - Seed Capital and Private Equity Investments (Details) - Other Assets - NAV - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Fair value		$ 223	$ 218
Unfunded commitments		81	82
Seed capital
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Fair value		90	101
Unfunded commitments		19	21
Private equity investments
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Fair value		129	113
Unfunded commitments		$ 62	$ 61
Fair value, investments, entities that calculate net asset value per share, liquidating investment, remaining period		10 years	10 years
Other
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Fair value		$ 4	$ 4
Unfunded commitments		$ 0	$ 0
Minimum | Seed capital
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Fair value, investments, entities that calculate net asset value per share, liquidating investment, remaining period	3 years	3 years
Maximum | Seed capital
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Fair value, investments, entities that calculate net asset value per share, liquidating investment, remaining period		11 years	11 years