Investment Securities - Components of Non-marketable and Other Equity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Investments in qualified affordable housing projects, net	$ 339,900	$ 318,575
Non-marketable and other equity securities	974,979	941,104
Fair value accounting | Consolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	108,404	118,333
Fair value accounting | Unconsolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	196,049	201,098
Fair value accounting | Other investments
Investment Holdings [Line Items]
Nonmarketable securities	37,796	25,668
Fair value accounting | Equity securities
Investment Holdings [Line Items]
Other equity securities in public companies (fair value accounting)	11,644	20,398
Equity method accounting | Consolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	148,096	129,485
Equity method accounting | Unconsolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	148,096	129,485
Equity method accounting | Other investments
Investment Holdings [Line Items]
Nonmarketable securities	127,264	121,721
Equity method accounting | Debt funds
Investment Holdings [Line Items]
Nonmarketable securities	$ 5,826	$ 5,826