Interim Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Impact of adopting ASC 326	Common Stock	Noncumulative Preferred Stock	Preferred Stock	Preferred Stock Noncumulative Preferred Stock	Common Stock	Common Stock Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Common Stock	Retained Earnings	Retained Earnings Impact of adopting ASC 326	Accumulated Other Comprehensive Income	Total SVBFG Stockholders’ Equity	Total SVBFG Stockholders’ Equity Impact of adopting ASC 326	Total SVBFG Stockholders’ Equity Common Stock	Total SVBFG Stockholders’ Equity Noncumulative Preferred Stock	Noncontrolling Interests
Balance (in shares) at Dec. 31, 2019							51,655,607
Balance, beginning of period, net of tax at Dec. 31, 2019	$ 6,621				$ 340		$ 0		$ 1,470		$ 4,576		$ 84	$ 6,470				$ 151
Balance, beginning of period, net of tax (Day one impact for adoption of ASC 326) at Dec. 31, 2019		$ (35)										$ (35)			$ (35)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee benefit plans, net of restricted stock cancellations (in shares)							376,588
Common stock issued under employee benefit plans, net of restricted stock cancellations	18						$ 0		18					18
Net income	855										815			815				40
Capital calls and distributions, net	(17)																	(17)
Other comprehensive (loss) income, net of tax	536												536	536
Share-based compensation, net	61								61					61
Common stock repurchases (in shares)							(244,223)
Common stock repurchases	(60)						$ 0				(60)			(60)
Dividends on preferred stock	(12)										(12)			(12)
Balance (in shares) at Sep. 30, 2020							51,787,972
Balance, end of period, net of tax at Sep. 30, 2020	7,967				340		$ 0		1,549		5,284		620	7,793				174
Balance (in shares) at Jun. 30, 2020							51,740,714
Balance, beginning of period, net of tax at Jun. 30, 2020	7,468				340		$ 0		1,523		4,842		614	7,319				149
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee benefit plans, net of restricted stock cancellations (in shares)							47,258
Common stock issued under employee benefit plans, net of restricted stock cancellations	4								4					4
Net income	474										446			446				28
Capital calls and distributions, net	(3)																	(3)
Other comprehensive (loss) income, net of tax	6
Share-based compensation, net	22								22					22
Dividends on preferred stock	(4)										(4)			(4)
Balance (in shares) at Sep. 30, 2020							51,787,972
Balance, end of period, net of tax at Sep. 30, 2020	7,967				340		$ 0		1,549		5,284		620	7,793				174
Balance (in shares) at Dec. 31, 2020							51,888,463
Balance, beginning of period, net of tax at Dec. 31, 2020	8,433				340		$ 0		1,585		5,672		623	8,220				213
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee benefit plans, net of restricted stock cancellations (in shares)							374,039
Common stock issued under employee benefit plans, net of restricted stock cancellations	(1)						$ 0		(1)					(1)
Issuance of stock			$ 2,363	$ 1,724				$ 0		$ 2,363						$ 2,363	$ 1,724
Issuance of stock (in shares)						1,724,000,000		4,527,000
Net income	1,665										1,439			1,439				226
Capital calls and distributions, net	(70)																	(70)
Other comprehensive (loss) income, net of tax	(558)													(558)
Share-based compensation, net	93								93					93
Dividends on preferred stock	(40)										40			(40)
Balance (in shares) at Sep. 30, 2021							58,677,483
Balance, end of period, net of tax at Sep. 30, 2021	14,669				2,064		$ 0		5,100		7,071		65	14,300				369
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for the acquisition of Boston Private (in shares)								1,887,981
Issuance of common stock for the acquisition of Boston Private			1,060					$ 0		1,060						1,060
Balance (in shares) at Jun. 30, 2021							54,530,307
Balance, beginning of period, net of tax at Jun. 30, 2021	11,967				2,064		$ 0		2,755		6,706		142	11,667				300
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee benefit plans, net of restricted stock cancellations (in shares)							32,195
Common stock issued under employee benefit plans, net of restricted stock cancellations	2								2					2
Issuance of stock			1,245					$ 0		1,245						1,245
Issuance of stock (in shares)								2,227,000
Net income	475										387			387				88
Capital calls and distributions, net	(19)																	(19)
Other comprehensive (loss) income, net of tax	(77)
Share-based compensation, net	38								38					38
Dividends on preferred stock	(22)										(22)			(22)
Balance (in shares) at Sep. 30, 2021							58,677,483
Balance, end of period, net of tax at Sep. 30, 2021	$ 14,669				$ 2,064		$ 0		$ 5,100		$ 7,071		$ 65	$ 14,300				$ 369
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for the acquisition of Boston Private (in shares)								1,887,981
Issuance of common stock for the acquisition of Boston Private			$ 1,060					$ 0		$ 1,060						$ 1,060