Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 30,912,438	$ 14,014,919
Fair Value, Derivative Assets	284,831	167,341
Fair Value, Derivative Liabilities	237,479	137,984
Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	0	22,676
Fair Value, Derivative Liabilities	0	25,623
Client interest rate derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	67,854	28,811
Fair Value, Derivative Liabilities	26,646	14,154
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	4,469,728	6,894,010
U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	237,307	99,547
Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	24,492	9,038
Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	13,503,681	4,148,791
Residential mortgage-backed securities | Fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	8,106,564	1,538,343
Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	4,570,666	1,325,190
Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	30,912,438	14,014,919
Total assets	31,955,334	14,672,330
Total liabilities	237,479	137,984
Measured on a recurring basis | 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	216,977	115,854
Measured on a recurring basis | Foreign exchange forward and option contracts | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	210,833	98,207
Measured on a recurring basis | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	203,438	165,473
Measured on a recurring basis | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets		22,676
Measured on a recurring basis | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities		25,623
Measured on a recurring basis | Client interest rate derivatives | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	67,854	28,811
Measured on a recurring basis | Client interest rate derivatives | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	26,646	14,154
Measured on a recurring basis | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonmarketable securities	554,627	324,597
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]
Nonmarketable securities		134
Measured on a recurring basis | Other securities | Fair value accounting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonmarketable securities	280,804	59,200
Measured on a recurring basis | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	4,469,728	6,894,010
Measured on a recurring basis | U.S. agency debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	237,307	99,547
Measured on a recurring basis | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	24,492	9,038
Measured on a recurring basis | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	13,503,681	4,148,791
Measured on a recurring basis | Residential mortgage-backed securities | Fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	8,106,564	1,538,343
Measured on a recurring basis | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	4,570,666	1,325,190
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]
Available-for-sale securities	4,494,220	6,903,048
Total assets	4,537,564	6,920,338
Total liabilities	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | 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) | Foreign exchange forward and option contracts | Other liabilities
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) | 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) | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets		0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities		0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | 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) | Client interest rate derivatives | Other liabilities
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]
Nonmarketable securities	43,344	17,290
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]
Nonmarketable securities		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]
Nonmarketable securities	43,344	17,290
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]
Available-for-sale securities	4,469,728	6,894,010
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]
Available-for-sale securities	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]
Available-for-sale securities	24,492	9,038
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential mortgage-backed securities | Fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	26,418,218	7,111,871
Total assets	26,951,730	7,325,557
Total liabilities	237,479	137,984
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | 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	216,977	115,854
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Foreign exchange forward and option contracts | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	210,833	98,207
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	11,221	4,435
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets		22,676
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities		25,623
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Client interest rate derivatives | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	67,854	28,811
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Client interest rate derivatives | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities	26,646	14,154
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]
Nonmarketable securities	237,460	41,910
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]
Nonmarketable securities		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]
Nonmarketable securities	237,460	41,910
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]
Available-for-sale securities	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]
Available-for-sale securities	237,307	99,547
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]
Available-for-sale securities	0	0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	13,503,681	4,148,791
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities | Fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	8,106,564	1,538,343
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	4,570,666	1,325,190
Measured on a recurring basis | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Total assets	192,217	161,172
Total liabilities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | 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) | Foreign exchange forward and option contracts | Other liabilities
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) | Equity warrant assets | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets	192,217	161,038
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Interest rate swaps | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Assets		0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Interest rate swaps | Other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Derivative Liabilities		0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | 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) | Client interest rate derivatives | Other liabilities
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]
Nonmarketable securities	0	134
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]
Nonmarketable securities		134
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]
Nonmarketable 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]
Available-for-sale securities	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]
Available-for-sale securities	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]
Available-for-sale securities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Residential mortgage-backed securities | Agency-issued mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Residential mortgage-backed securities | Fixed rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Agency-issued commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Measured on a recurring basis | 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]
Nonmarketable securities	$ 273,823	$ 265,263