Investment Securities - Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	$ 138,575	$ 88,834	$ 69,792
Losses on sales of securities	5,200
OTTI	400	5,300	4,200
Gains on sales of investments		20,800	3,800
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	(4,744)	26,097	355
Net gains on non-marketable and other equity securities still held	133,831	114,931	70,147
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	22,507	20,999	27,186
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	73,813	49,341	14,472
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	31,482	39,075	21,377
Non-marketable securities | Other investments | Fair value accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	2,742	3,206	3,842
Non-marketable securities | Other investments | Equity method accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	(1,388)	1,155	(6,276)
Non-marketable securities | Debt funds | Equity method accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	1,647	541	8,950
Other equity securities | Fair value accounting
Gain (Loss) on Securities [Line Items]
Gains on non-marketable and other equity securities, net	$ 7,772	$ (25,483)	$ 241