Investment Securities - Net Gains on Non-marketable and Other Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	$ (15,110)	$ 32,658
Non-marketable securities
Gain (Loss) on Securities [Line Items]
Less: realized net (losses) gains on sales of non-marketable and other equity securities	(49)	9,835
Net (losses) gains on non-marketable and other equity securities still held	(15,061)	22,823
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	3,113	3,289
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	1,252	8,006
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	(2,943)	5,005
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	(8,046)	2,789
Non-marketable securities | Equity method accounting | Debt funds
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	(362)	0
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	(620)	1,766
Other equity securities | Fair value accounting
Gain (Loss) on Securities [Line Items]
Total net gains on non-marketable and other equity securities	$ (7,504)	$ 11,803