Investment Securities - Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	$ 359,587	$ 138,575	$ 88,834
Non-marketable securities
Gain (Loss) on Securities [Line Items]
Less: Realized net losses on the sales and OTTI of non-marketable and other equity securities	(23,344)	(4,744)	26,097
Net gains on non-marketable and other equity securities still held	336,243	133,831	114,931
Non-marketable securities | Consolidated venture capital and private equity fund investments | Fair value accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	32,439	22,507	20,999
Non-marketable securities | Consolidated venture capital and private equity fund investments | Equity method accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	161,828	73,813	49,341
Non-marketable securities | Unconsolidated venture capital and private equity fund investments | Fair value accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	59,909	31,482	39,075
Non-marketable securities | Other investments | Fair value accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	253	2,742	3,206
Non-marketable securities | Other investments | Equity method accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	696	(1,388)	1,155
Non-marketable securities | Debt funds | Equity method accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	(403)	1,647	541
Other equity securities | Fair value accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	$ 104,865	$ 7,772	$ (25,483)