Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 7,790,043	$ 11,120,664
Fair Value, Derivative Assets	108,901	108,389
Fair Value, Derivative Liabilities	98,050	108,581
Client interest rate derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	8,499	11,753
Fair Value, Derivative Liabilities	9,491	11,940
Derivatives not designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	258,139	232,152
Fair Value, Derivative Liabilities	98,050	108,581
Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	149,238	123,763
Derivatives not designated as hedging instruments | Client interest rate derivatives | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	8,499	11,753
Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	9,491	11,940
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,738,258	6,840,502
U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,084,117	1,567,128
Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	5,812
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value		72,269
Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	7,790,043	11,120,664
Total assets	8,388,011	11,481,237
Total liabilities	98,050	108,581
Measured on a recurring basis | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	100,402	96,636
Measured on a recurring basis | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	88,559	96,641
Measured on a recurring basis | Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	149,238	123,763
Measured on a recurring basis | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	8,499	11,753
Measured on a recurring basis | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	9,491	11,940
Measured on a recurring basis | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	339,829	128,421
Measured on a recurring basis | Consolidated venture capital and private equity fund investments | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	1,079	919
Measured on a recurring basis | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	20,398	310
Measured on a recurring basis | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,738,258	6,840,502
Measured on a recurring basis | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,084,117	1,567,128
Measured on a recurring basis | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	5,812
Measured on a recurring basis | Fixed rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,880,218	2,267,035
Measured on a recurring basis | Variable rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	81,638	373,730
Measured on a recurring basis | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value		72,269
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,744,070	6,840,660
Total assets	4,745,251	6,840,970
Total liabilities	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	1,181	310
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Consolidated venture capital and private equity fund investments | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	1,181	310
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,738,258	6,840,502
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	5,812
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Variable rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value		158
Measured on a recurring basis | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	3,045,973	4,280,004
Total assets	3,178,130	4,390,825
Total liabilities	98,050	108,581
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	100,402	96,636
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	88,559	96,641
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	4,039	2,432
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	8,499	11,753
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	9,491	11,940
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	19,217	0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Consolidated venture capital and private equity fund investments | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	0	0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	19,217	0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,084,117	1,567,128
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Fixed rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,880,218	2,267,035
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Variable rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	81,638	373,730
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value		72,111
Measured on a recurring basis | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Total assets	146,278	122,250
Total liabilities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Derivatives not designated as hedging instruments | Foreign exchange forward and option contracts | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	145,199	121,331
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	1,079	919
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Consolidated venture capital and private equity fund investments | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	1,079	919
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Fixed rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Variable rate | Agency-issued collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value		0
Measured on a recurring basis | Measured at net asset value | Consolidated venture capital and private equity fund investments | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	$ 318,352	$ 127,192