Investment Securities - Carrying Value and Ownership Percentage of Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Consolidated venture capital and private equity fund investments | Fair value accounting
Investment Holdings [Line Items]
Nonmarketable securities	$ 96,016		$ 88,937
Consolidated venture capital and private equity fund investments | Fair value accounting | Strategic Investors Fund, LP
Investment Holdings [Line Items]
Nonmarketable securities	5,165		4,850
Consolidated venture capital and private equity fund investments | Fair value accounting | Capital Preferred Return Fund, LP
Investment Holdings [Line Items]
Nonmarketable securities	48,572		49,574
Consolidated venture capital and private equity fund investments | Fair value accounting | Growth Partners, LP
Investment Holdings [Line Items]
Nonmarketable securities	42,279		34,513
Consolidated venture capital and private equity fund investments | Equity method accounting
Investment Holdings [Line Items]
Nonmarketable securities	394,349		362,192
Consolidated venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund II, LP
Investment Holdings [Line Items]
Nonmarketable securities	4,624		3,705
Consolidated venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund III, LP
Investment Holdings [Line Items]
Nonmarketable securities	21,281		16,110
Consolidated venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund IV, LP
Investment Holdings [Line Items]
Nonmarketable securities	29,681		25,169
Consolidated venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund V funds
Investment Holdings [Line Items]
Nonmarketable securities	60,992		67,052
Consolidated venture capital and private equity fund investments | Equity method accounting | CP II, LP
Investment Holdings [Line Items]
Nonmarketable securities	8,954		7,887
Consolidated venture capital and private equity fund investments | Equity method accounting | Other venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	268,817		242,269
Debt funds | Equity method accounting
Investment Holdings [Line Items]
Nonmarketable securities	5,813		5,444
Debt funds | Equity method accounting | Gold Hill Capital 2008, LP
Investment Holdings [Line Items]
Nonmarketable securities	4,380		3,941
Debt funds | Equity method accounting | Other debt funds
Investment Holdings [Line Items]
Nonmarketable securities	1,433		1,503
Other investments | Fair value accounting
Investment Holdings [Line Items]
Nonmarketable securities	200,367		60,975
Other investments | Equity method accounting
Investment Holdings [Line Items]
Nonmarketable securities	205,002		202,809
Other investments | Equity method accounting | SPD Silicon Valley Bank Co., Ltd.
Investment Holdings [Line Items]
Nonmarketable securities	111,838		115,232
Other investments | Equity method accounting | Other investments
Investment Holdings [Line Items]
Nonmarketable securities	$ 93,164		$ 87,577
Non-marketable securities | Consolidated venture capital and private equity fund investments | Fair value accounting | Strategic Investors Fund, LP
Investment Holdings [Line Items]
Percentage of ownership	12.60%	12.60%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Fair value accounting | Capital Preferred Return Fund, LP
Investment Holdings [Line Items]
Percentage of ownership	20.00%	20.00%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Fair value accounting | Growth Partners, LP
Investment Holdings [Line Items]
Percentage of ownership	33.00%	33.00%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund II, LP
Investment Holdings [Line Items]
Percentage of ownership	8.60%	8.60%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund III, LP
Investment Holdings [Line Items]
Percentage of ownership	5.90%	5.90%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund IV, LP
Investment Holdings [Line Items]
Percentage of ownership	5.00%	5.00%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Equity method accounting | CP II, LP
Investment Holdings [Line Items]
Percentage of ownership	5.10%	5.10%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Equity method accounting | CP II, LP | Direct ownership interest
Investment Holdings [Line Items]
Percentage of ownership	1.30%
Non-marketable securities | Consolidated venture capital and private equity fund investments | Equity method accounting | CP II, LP | Indirect ownership interest
Investment Holdings [Line Items]
Percentage of ownership	3.80%
Non-marketable securities | Debt funds | Equity method accounting | Direct ownership interest
Investment Holdings [Line Items]
Percentage of ownership	11.50%
Non-marketable securities | Debt funds | Equity method accounting | Indirect ownership interest
Investment Holdings [Line Items]
Percentage of ownership	4.00%
Non-marketable securities | Debt funds | Equity method accounting | Gold Hill Capital 2008, LP
Investment Holdings [Line Items]
Percentage of ownership	15.50%	15.50%
Non-marketable securities | Other investments | Equity method accounting | SPD Silicon Valley Bank Co., Ltd.
Investment Holdings [Line Items]
Percentage of ownership	50.00%	50.00%