Investment Securities - Components of Non-marketable and Other Equity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Investments in qualified affordable housing projects, net	$ 394,046	$ 318,575
Non-marketable and other equity securities	1,079,749	941,104
Fair value accounting | Consolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	110,086	118,333
Fair value accounting | Unconsolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	193,206	201,098
Fair value accounting | Other investments
Investment Holdings [Line Items]
Nonmarketable securities	42,419	25,668
Fair value accounting | Equity securities
Investment Holdings [Line Items]
Other equity securities in public companies (fair value accounting)	39,808	20,398
Equity method accounting | Consolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	169,219	129,485
Equity method accounting | Unconsolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	169,219	129,485
Equity method accounting | Other investments
Investment Holdings [Line Items]
Nonmarketable securities	123,797	121,721
Equity method accounting | Debt funds
Investment Holdings [Line Items]
Nonmarketable securities	$ 7,168	$ 5,826