Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	$ 36,727,222		$ 33,164,636
Allowance for credit losses	(589,828)	$ (548,963)	(304,924)	$ (301,888)	$ (300,151)	$ (280,903)
Net loans	36,137,394		32,859,712
Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	17,901,117		17,696,794
Allowance for credit losses	(53,723)	(56,774)	(107,285)	(101,253)	(95,311)	(93,781)
Investor dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	5,138,876		4,335,195
Allowance for credit losses	(292,267)	(275,701)	(82,370)	(97,173)	(95,056)	(72,101)
Investor dependent | Early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,797,576		1,624,221
Allowance for credit losses	(148,270)	(127,189)	(26,245)	(30,969)	(26,730)	(25,885)
Investor dependent | Mid stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,435,772		1,047,398
Allowance for credit losses	(56,393)	(51,962)	(15,936)	(28,264)	(38,163)	(20,999)
Investor dependent | Later stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,905,528		1,663,576
Allowance for credit losses	(87,604)	(96,550)	(40,189)	(37,940)	(30,163)	(25,217)
Cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	4,845,246		4,424,238
Allowance for credit losses	(97,953)	(81,507)	(68,098)	(56,682)	(61,447)	(66,028)
Cash flow dependent | Sponsor led buyout
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,057,439		2,185,497
Allowance for credit losses	(54,853)	(42,091)	(42,939)	(32,131)	(40,933)	(44,274)
Cash flow dependent | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,787,807		2,238,741
Allowance for credit losses	(43,100)	(39,416)	(25,159)	(24,551)	(20,514)	(21,754)
SVB Private Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	3,816,277		3,492,269
Allowance for credit losses	(91,345)	(87,795)	(21,551)	(20,397)	(19,964)	(20,583)
Balance sheet dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,693,071		1,286,153
Allowance for credit losses	(24,728)	(23,235)	(12,722)	(17,256)	(21,632)	(21,707)
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,039,456		1,062,264
Allowance for credit losses	(12,319)	(12,377)	(5,296)	(4,227)	(3,949)	(3,646)
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	457,234		867,723
Allowance for credit losses	(13,635)	(11,574)	(7,602)	$ (4,900)	$ (2,792)	$ (3,057)
SBA loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,835,945		0
Allowance for credit losses	$ (3,858)	$ 0	$ 0