Basis of Presentation - Adoption of New Accounting Standards (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable		$ 61,090		$ 61,090		$ 21,606	$ 55,946
Deferred fees		556		556		736	27,057
Current taxes payable		2,002		2,002		2,458	4,675
Retained earnings		3,672,696		3,672,696		2,861,035	2,866,837
Fund management fees		5,479		17,144
Income tax expense		95,308	$ 97,351	246,561	$ 220,412
Net income available to common stockholders		$ 274,817	$ 148,620	$ 707,576	$ 373,296
Diluted (dollars per share)		$ 5.10	$ 2.79	$ 13.15	$ 7.01
Reclassification of stranded tax effect for ASU 2018-02	[1]	$ 0	$ 0	$ 319	$ 0
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable							(34,340)
Deferred fees							(26,321)
Current taxes payable							(2,217)
Retained earnings							(5,802)
Cumulative adjustment for ASU, net of tax	[2]						(5,802)
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 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for ASU, net of tax	[2]						74,595
Total SVBFG Stockholders’ Equity | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for ASU, net of tax	[2]						(5,802)
Total SVBFG Stockholders’ Equity | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for ASU, net of tax						74,600	74,595	[2]
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effect for ASU 2018-02	[2]			(319)
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for ASU, net of tax						$ (29,200)	$ (29,171)	[2]
Balances Without Adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable		100,470		100,470
Deferred fees		28,379		28,379
Current taxes payable		(694)		(694)
Retained earnings		3,678,020		3,678,020
Fund management fees		6,087		19,001
Income tax expense		95,463		247,040
Net income available to common stockholders		$ 275,270		$ 708,954
Diluted (dollars per share)		$ 5.11		$ 13.18
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable		$ (39,380)		$ (39,380)
Deferred fees		(27,823)		(27,823)
Current taxes payable		2,696		2,696
Retained earnings		(5,324)		(5,324)
Fund management fees		(608)		(1,857)
Income tax expense		(155)		(479)
Net income available to common stockholders		$ (453)		$ (1,378)
Diluted (dollars per share)		$ (0.01)		$ (0.03)

[1] See "Adoption of New Accounting Standards" in Note 1—“Basis of Presentation” of the “Notes to Interim Consolidated Financial Statements (unaudited)” under Part I, Item 1 of this report for additional details.

[2] See "Adoption of New Accounting Standards" in Note 1—“Basis of Presentation” of the “Notes to Interim Consolidated Financial Statements (unaudited)” under Part I, Item 1 of this report for additional details.