Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) portfolio_segment class_financing_receivable risk_based_segment	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	$ 38,413,891		$ 33,164,636
Allowance for credit losses	(512,958)	$ (589,828)	(304,924)	$ (304,410)	$ (301,888)	$ (280,903)
Net loans	$ 37,900,933		32,859,712
Number of portfolio segments | portfolio_segment	6
Number of financing receivable classes | class_financing_receivable	10
Number of risk-based segments | risk_based_segment	11
Global fund banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	$ 19,584,518		17,696,794
Allowance for credit losses	(38,989)	(53,723)	(107,285)	(103,916)	(101,253)	(93,781)
Investor dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	5,111,669		4,335,195
Allowance for credit losses	(262,688)	(292,267)	(82,370)	(92,685)	(97,173)	(72,101)
Investor dependent | Early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,470,941		1,624,221
Allowance for credit losses	(102,559)	(148,270)	(26,245)	(30,903)	(30,969)	(25,885)
Investor dependent | Mid stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,626,794		1,047,398
Allowance for credit losses	(62,418)	(56,393)	(15,936)	(17,761)	(28,264)	(20,999)
Investor dependent | Later stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,013,934		1,663,576
Allowance for credit losses	(97,711)	(87,604)	(40,189)	(44,021)	(37,940)	(25,217)
Cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	4,662,400		4,424,238
Allowance for credit losses	(91,982)	(97,953)	(68,098)	(63,300)	(56,682)	(66,028)
Cash flow dependent | Sponsor led buyout
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,062,243		2,185,497
Allowance for credit losses	(51,661)	(54,853)	(42,939)	(41,651)	(32,131)	(44,274)
Cash flow dependent | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,600,157		2,238,741
Allowance for credit losses	(40,321)	(43,100)	(25,159)	(21,649)	(24,551)	(21,754)
SVB Private Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	4,424,899		3,492,269
Allowance for credit losses	(76,479)	(91,345)	(21,551)	(21,700)	(20,397)	(20,583)
Balance sheet dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,698,220		1,286,153
Allowance for credit losses	(29,069)	(24,728)	(12,722)	(14,797)	(17,256)	(21,707)
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,081,963		1,062,264
Allowance for credit losses	(10,405)	(12,319)	(5,296)	(4,254)	(4,227)	(3,646)
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	48,206		867,723
Allowance for credit losses	(866)	(13,635)	(7,602)	$ (3,758)	$ (4,900)	$ (3,057)
SBA loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,802,016		0
Allowance for credit losses	$ (2,480)	$ (3,858)	$ 0