Investment Securities - Net Gains on Non-marketable and Other Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	$ 34,868	$ 47,973	$ 19,758	$ 80,631
Non-marketable securities
Gain (Loss) on Securities [Line Items]
Less: realized net gains on sales of non-marketable and other equity securities	264	2,524	215	12,359
Net gains on non-marketable and other equity securities still held	34,604	45,449	19,543	68,272
Non-marketable securities | Fair value accounting | Consolidated venture capital and private equity fund investments
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	1,277	14,830	4,390	18,119
Non-marketable securities | Fair value accounting | Unconsolidated venture capital and private equity fund investments
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	(2,465)	10,152	(1,213)	18,158
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	(893)	167	(3,836)	5,172
Non-marketable securities | Equity method accounting | Consolidated venture capital and private equity fund investments
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	26,393	22,351	18,347	25,140
Non-marketable securities | Equity method accounting | Debt funds
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	94	1,342	(268)	1,342
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	(2,526)	(1,151)	(3,146)	615
Other equity securities | Fair value accounting
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	$ 12,988	$ 282	$ 5,484	$ 12,085