Investment Securities - Summary of Venture Capital and Private Equity Fund Investments Held by Consolidated Funds and Percentage Ownership (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Upper Limit
Investment Holdings [Line Items]
Percentage of ownership	5.00%
Fair value accounting | Consolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	$ 174		$ 130
Fair value accounting | Consolidated venture capital and private equity fund investments | Redwood Evergreen Fund, LP
Investment Holdings [Line Items]
Nonmarketable securities	60		0
Fair value accounting | Consolidated venture capital and private equity fund investments | Strategic Investors Fund, LP
Investment Holdings [Line Items]
Nonmarketable securities	2		2
Fair value accounting | Consolidated venture capital and private equity fund investments | Capital Preferred Return Fund, LP
Investment Holdings [Line Items]
Nonmarketable securities	53		61
Fair value accounting | Consolidated venture capital and private equity fund investments | Growth Partners, LP
Investment Holdings [Line Items]
Nonmarketable securities	$ 59		$ 67
Non-marketable securities | Fair value accounting | Consolidated venture capital and private equity fund investments | Redwood Evergreen Fund, LP
Investment Holdings [Line Items]
Percentage of ownership	100.00%	0.00%
Non-marketable securities | Fair value accounting | Consolidated venture capital and private equity fund investments | Strategic Investors Fund, LP
Investment Holdings [Line Items]
Percentage of ownership	12.60%	12.60%
Non-marketable securities | Fair value accounting | Consolidated venture capital and private equity fund investments | Capital Preferred Return Fund, LP
Investment Holdings [Line Items]
Percentage of ownership	20.00%	20.00%
Non-marketable securities | Fair value accounting | Consolidated venture capital and private equity fund investments | Growth Partners, LP
Investment Holdings [Line Items]
Percentage of ownership	33.00%	33.00%