Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 25,904,324	$ 25,904,324	$ 14,014,919
Derivative Assets	224,861	224,861	167,341
Derivative Liabilities	137,781	137,781	137,984
Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	22,676
Derivative Liabilities	0	0	25,623
Client interest rate derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	79,270	79,270	28,811
Derivative Liabilities	25,558	25,558	14,154
Derivatives not designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	427,045	427,045	310,138
Derivative Liabilities	137,781	137,781	112,361
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	202,184	202,184	165,473
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	79,270	79,270	28,811
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	25,558	25,558	14,154
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,547,294	4,547,294	6,894,010
U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	152,526	152,526	99,547
Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	23,449	23,449	9,038
Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	9,770,313	9,770,313	4,148,791
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	7,315,973	7,315,973	1,538,343
Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,094,769	4,094,769	1,325,190
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	25,904,324	25,904,324	14,014,919
Total assets	26,787,326	26,787,326	14,672,330
Total liabilities	137,781	137,781	137,984
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	145,591	145,591	115,854
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	112,223	112,223	98,207
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	202,184	202,184	165,473
Recurring | Derivatives not designated as hedging instruments | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets			22,676
Recurring | Derivatives not designated as hedging instruments | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities			25,623
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	79,270	79,270	28,811
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	25,558	25,558	14,154
Recurring | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	455,957	455,957	324,597
Recurring | 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	134	134	134
Recurring | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	229,297	229,297	59,200
Recurring | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,547,294	4,547,294	6,894,010
Recurring | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	152,526	152,526	99,547
Recurring | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	23,449	23,449	9,038
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	9,770,313	9,770,313	4,148,791
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	7,315,973	7,315,973	1,538,343
Recurring | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,094,769	4,094,769	1,325,190
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,570,743	4,570,743	6,903,048
Total assets	4,596,948	4,596,948	6,920,338
Total liabilities	0	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	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	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	0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets			0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities			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	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	0
Recurring | Level 1 | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	26,205	26,205	17,290
Recurring | 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	0
Recurring | Level 1 | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	26,205	26,205	17,290
Recurring | Level 1 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,547,294	4,547,294	6,894,010
Recurring | Level 1 | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0	0
Recurring | Level 1 | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	23,449	23,449	9,038
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	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	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	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	21,333,581	21,333,581	7,111,871
Total assets	21,771,035	21,771,035	7,325,557
Total liabilities	137,781	137,781	137,984
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	145,591	145,591	115,854
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	112,223	112,223	98,207
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	9,501	9,501	4,435
Recurring | Level 2 | Derivatives not designated as hedging instruments | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets			22,676
Recurring | Level 2 | Derivatives not designated as hedging instruments | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities			25,623
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	79,270	79,270	28,811
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	25,558	25,558	14,154
Recurring | Level 2 | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	203,092	203,092	41,910
Recurring | 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	0
Recurring | Level 2 | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	203,092	203,092	41,910
Recurring | Level 2 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0	0
Recurring | Level 2 | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	152,526	152,526	99,547
Recurring | Level 2 | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	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	9,770,313	9,770,313	4,148,791
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	7,315,973	7,315,973	1,538,343
Recurring | Level 2 | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	4,094,769	4,094,769	1,325,190
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	0	0	0
Total assets	192,817	192,817	161,172
Total liabilities	0	0	0
Recurring | Level 3 | Noncontrolling Interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	120	120	120
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	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	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	192,683	192,683	161,038
Recurring | Level 3 | Derivatives not designated as hedging instruments | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets			0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities			0
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	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	0
Recurring | Level 3 | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable securities	134	134	134
Recurring | 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	134	134	134
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	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	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	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	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	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	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	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	$ 226,526	$ 226,526	$ 265,263
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 | Lower Limit | Other equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.10	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	0.100	0.100	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	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	0.200	0.200	0.200