Summary of Significant Accounting Policies - Adoption of New Accounting Standards (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended									12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable		$ 55,807				$ 55,946					$ 55,807		$ 55,946			$ 21,606
Deferred revenue		598				27,057					598		27,057			736
Current taxes payable		3,330				4,675					3,330		4,675			2,458
Retained earnings		3,791,838				2,866,837					3,791,838		2,866,837			2,861,035
Fund management fees											23,016		21,214		$ 19,195
Income tax expense		105,000	$ 95,308	$ 77,287	$ 73,966	135,051		$ 97,351	$ 71,656	$ 51,405	351,561	[1]	355,463	[1]	250,333
Net income available to common stockholders		$ 266,264	$ 274,817	$ 237,798	$ 194,961	$ 117,210		$ 148,620	$ 123,193	$ 101,483	$ 973,840	[1]	$ 490,506	[1]	$ 382,685
Earnings per common share—diluted (usd per share)		$ 4.96	$ 5.10	$ 4.42	$ 3.63	$ 2.19		$ 2.79	$ 2.32	$ 1.91	$ 18.11	[1]	$ 9.20	[1]	$ 7.31
Reclassification of stranded tax effect for ASU 2018-02	[2]										$ 319		$ 0		$ 0
Balances Without Adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable		$ 96,479									96,479
Deferred revenue		28,478									28,478
Current taxes payable		531									531
Retained earnings		3,799,255									3,799,255
Fund management fees											25,213
Income tax expense											352,143
Net income available to common stockholders											$ 975,455
Earnings per common share—diluted (usd per share)											$ 18.14
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable						$ (34,340)							(34,340)
Deferred revenue						(26,321)							(26,321)
Current taxes payable						(2,217)							(2,217)
Retained earnings						(5,802)							(5,802)
Cumulative adjustment for new accounting standards	[3]					(5,802)							(5,802)
Accounting Standards Update 2014-09 | Total SVBFG Stockholders’ Equity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for new accounting standards	[3]					(5,802)							(5,802)
Accounting Standards Update 2014-09 | Effect of Change Higher/(Lower)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable		(40,672)									$ (40,672)
Deferred revenue		(27,880)									(27,880)
Current taxes payable		2,799									2,799
Retained earnings		$ (7,417)									(7,417)
Fund management fees											(2,197)
Income tax expense											(582)
Net income available to common stockholders											$ (1,615)
Earnings per common share—diluted (usd per share)											$ (0.03)
Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effect for ASU 2018-02											$ 300
Accounting Standards Update 2018-02 | Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effect for ASU 2018-02	[3]										$ 319
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for new accounting standards	[3]					74,595							74,595
Accounting Standards Update 2016-01 | Total SVBFG Stockholders’ Equity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for new accounting standards						74,595	[3]						74,595	[3]		74,600
Accounting Standards Update 2016-01 | Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for new accounting standards						$ (29,171)	[3]						$ (29,171)	[3]		$ (29,200)

[1] Included in income tax expense, net income available to common stockholders, earnings per common share-basic and earnings for common share-diluted, for the years ended December 31, 2018 and 2017, are tax benefits recognized associated with the adoption of Accounting Standards Update ("ASU") 2016-09, Improvements to Employee Share-Based Payment Accounting in the first quarter of 2017. This guidance was adopted on a prospective basis with no change to prior period amounts.

[2] See Note 2- "Summary of Significant Accounting Policies" of the "Notes to Consolidated Financial Statements" under Part II, Item 8 of this report for additional details.

[3] See Note 2- "Summary of Significant Accounting Policies" of the "Notes to Consolidated Financial Statements" under Part II, Item 8 of this report for additional details.