Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 25,986,471	$ 30,912,438
Derivative Assets	305,306	284,831
Derivative Liabilities	271,486	237,479
Client interest rate derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	65,123	67,854
Derivative Liabilities	68,954	26,646
Derivatives not designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	549,640	488,269
Derivative Liabilities	271,486	237,479
Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	244,334	203,438
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]
Derivative Assets	65,123	67,854
Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	68,954	26,646
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,438,396	4,469,728
U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	226,095	237,307
Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	23,450	24,492
Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	12,514,911	13,503,681
Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	7,256,626	8,106,564
Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,526,993	4,570,666
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	25,986,471	30,912,438
Total assets	26,971,345	31,955,334
Total liabilities	271,486	237,479
Recurring | Derivatives not designated as hedging instruments | Foreign exchange contract | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	240,183	216,977
Recurring | Derivatives not designated as hedging instruments | Foreign exchange contract | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	202,532	210,833
Recurring | Derivatives not designated as hedging instruments | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	244,334	203,438
Recurring | 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]
Derivative Assets	65,123	67,854
Recurring | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	68,954	26,646
Recurring | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	435,234	554,627
Recurring | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	160,810	280,804
Recurring | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,438,396	4,469,728
Recurring | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	226,095	237,307
Recurring | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	23,450	24,492
Recurring | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	12,514,911	13,503,681
Recurring | Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	7,256,626	8,106,564
Recurring | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,526,993	4,570,666
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,461,846	4,494,220
Total assets	4,500,099	4,537,564
Total liabilities	0	0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Foreign exchange contract | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Foreign exchange contract | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0	0
Recurring | 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]
Derivative Assets	0	0
Recurring | 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]
Derivative Assets	0	0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0	0
Recurring | Level 1 | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	38,253	43,344
Recurring | Level 1 | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	38,253	43,344
Recurring | Level 1 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,438,396	4,469,728
Recurring | Level 1 | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 1 | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	23,450	24,492
Recurring | Level 1 | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 1 | Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 1 | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	21,524,625	26,418,218
Total assets	21,963,440	26,951,730
Total liabilities	271,486	237,479
Recurring | Level 2 | Derivatives not designated as hedging instruments | Foreign exchange contract | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	240,183	216,977
Recurring | Level 2 | Derivatives not designated as hedging instruments | Foreign exchange contract | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	202,532	210,833
Recurring | 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]
Derivative Assets	10,952	11,221
Recurring | 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]
Derivative Assets	65,123	67,854
Recurring | Level 2 | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	68,954	26,646
Recurring | Level 2 | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	122,557	237,460
Recurring | Level 2 | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	122,557	237,460
Recurring | Level 2 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 2 | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	226,095	237,307
Recurring | Level 2 | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 2 | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	12,514,911	13,503,681
Recurring | Level 2 | Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	7,256,626	8,106,564
Recurring | Level 2 | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,526,993	4,570,666
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Total assets	233,382	192,217
Total liabilities	0	0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Foreign exchange contract | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Foreign exchange contract | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0	0
Recurring | 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]
Derivative Assets	233,382	192,217
Recurring | 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]
Derivative Assets	0	0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Client interest rate derivatives | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0	0
Recurring | Level 3 | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	0	0
Recurring | 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
Recurring | Level 3 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 3 | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 3 | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 3 | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 3 | Residential mortgage-backed securities | Agency-issued collateralized mortgage obligations—fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | Level 3 | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0
Recurring | 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	$ 274,424	$ 273,823
Lower Limit | Other equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, sales restriction, period	3 years
Lower Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, sales restriction, period	3 months
Upper Limit | Other equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, sales restriction, period	6 months
Upper Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, sales restriction, period	6 months
Sales restrictions discount | Level 3 | Equity warrant asset, public portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.100
Sales restrictions discount | Lower Limit | Other equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.10
Sales restrictions discount | Lower Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.10	0.100
Sales restrictions discount | Upper Limit | Other equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.20
Sales restrictions discount | Upper Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.20	0.200