Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Commitments to Invest in Venture Capital and Private Equity Funds (Additional Information) (Details) $ in Millions	3 Months Ended
	Jun. 30, 2022 USD ($) Investment	Jun. 30, 2021
Parent Company
Venture Capital and Private Equity Fund Investments [Line Items]
Unfunded commitments	$ 172
Parent Company | Redwood Evergreen Fund, LP
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	100.00%
Unfunded commitments	$ 150
Upper Limit
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	5.00%
CP II, LP | Parent Company
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	5.10%
Unfunded commitments	$ 0
Other fund investments | Parent Company
Venture Capital and Private Equity Fund Investments [Line Items]
Unfunded commitments	$ 11
Consolidated venture capital and private equity fund investments
Venture Capital and Private Equity Fund Investments [Line Items]
Commitments to invest, period from the inception of the fund	10 years
Call unrestricted, percentage of committed capital	100.00%
Unfunded commitments	$ 3
Consolidated venture capital and private equity fund investments | Lower Limit
Venture Capital and Private Equity Fund Investments [Line Items]
Expected commitment period to invest in venture capital and private equity funds (in years)	5 years
Consolidated venture capital and private equity fund investments | Upper Limit
Venture Capital and Private Equity Fund Investments [Line Items]
Expected commitment period to invest in venture capital and private equity funds (in years)	7 years
Consolidated venture capital and private equity fund investments | Non-marketable securities | Equity method accounting | CP II, LP
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	5.10%	5.10%
Consolidated venture capital and private equity fund investments | Non-marketable securities | Equity method accounting | Other fund investments
Venture Capital and Private Equity Fund Investments [Line Items]
Number of other funds with investment commitments | Investment	148
Consolidated venture capital and private equity fund investments | Non-marketable securities | Direct ownership interest | Equity method accounting | CP II, LP
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	1.30%
Consolidated venture capital and private equity fund investments | Non-marketable securities | Indirect ownership interest | Equity method accounting | CP II, LP
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	3.80%