Parent Company Only Condensed Financial Information - Condensed Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Statement of Income Captions [Line Items]
Changes in fair value on bank cash flow hedges, net of reclassification adjustments in bank net income	$ 129,300
Other comprehensive income (loss), net of tax	538,072	$ 138,565	$ (52,648)
Comprehensive income attributable to SVBFG	1,746,440	1,275,421	921,192
Parent Company
Condensed Statement of Income Captions [Line Items]
Net income before preferred stock dividend	1,208,368	1,136,856	973,840
Foreign currency translation gains (losses)	11,846	2,319	(4,107)
Changes in unrealized holding gains and losses on AFS securities	70	2,310	120
Changes in fair value on bank cash flow hedges, net of reclassification adjustments in bank net income	131,403	(2,130)	0
Equity in other comprehensive income (loss) of bank and nonbank subsidiaries	394,753	136,066	(19,171)
Reclassifications to retained earnings for the adoption of new accounting guidance	0	0	(29,490)
Other comprehensive income (loss), net of tax	538,072	138,565	(52,648)
Comprehensive income attributable to SVBFG	$ 1,746,440	$ 1,275,421	$ 921,192