Investment Securities - Major Components of Non-marketable and Other Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Investments in qualified affordable housing projects, net	$ 318,575	$ 174,214
Total non-marketable and other securities	941,104	651,053
Consolidated venture capital and private equity fund investments | Fair value accounting
Investment Holdings [Line Items]
Nonmarketable securities	118,333	128,111
Consolidated venture capital and private equity fund investments | Equity method accounting
Investment Holdings [Line Items]
Nonmarketable securities	129,485	89,809
Unconsolidated venture capital and private equity fund investments | Fair value accounting
Investment Holdings [Line Items]
Nonmarketable securities	201,098	98,548
Unconsolidated venture capital and private equity fund investments | Equity method accounting
Investment Holdings [Line Items]
Nonmarketable securities	129,485	89,809
Other investments | Fair value accounting
Investment Holdings [Line Items]
Nonmarketable securities	25,668	27,680
Other investments | Equity method accounting
Investment Holdings [Line Items]
Nonmarketable securities	121,721	111,198
Equity securities | Fair value accounting
Investment Holdings [Line Items]
Other equity securities	20,398	310
Debt funds | Equity method accounting
Investment Holdings [Line Items]
Nonmarketable securities	$ 5,826	$ 21,183