Stockholders' Equity and EPS - QTD Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stockholders Equity Note [Line Items]
Balance, beginning of period, net of tax	$ 11,967	$ 7,468	$ 8,433	$ 6,621
Common stock issued under employee benefit plans, net of restricted stock cancellations	2	4	(1)	18
Net income	475	474	1,665	855
Capital calls and distributions, net	(19)	(3)	(70)	(17)
Other comprehensive income, net of tax	(77)	6
Share-based compensation, net	38	22	93	61
Dividends on preferred stock	(22)	(4)	(40)	(12)
Balance, end of period, net of tax	14,669	7,967	14,669	7,967
Common Stock
Stockholders Equity Note [Line Items]
Issuance of stock	1,245		2,363
Issuance of common stock for the acquisition of Boston Private	1,060		1,060
Noncumulative Preferred Stock
Stockholders Equity Note [Line Items]
Issuance of stock			1,724
Preferred Stock
Stockholders Equity Note [Line Items]
Balance, beginning of period, net of tax	2,064	340	340	340
Balance, end of period, net of tax	$ 2,064	$ 340	$ 2,064	$ 340
Preferred Stock | Noncumulative Preferred Stock
Stockholders Equity Note [Line Items]
Issuance of stock (in shares)			1,724,000,000
Common Stock
Stockholders Equity Note [Line Items]
Balance (in shares)	54,530,307	51,740,714	51,888,463	51,655,607
Balance, beginning of period, net of tax	$ 0	$ 0	$ 0	$ 0
Common stock issued under employee benefit plans, net of restricted stock cancellations (in shares)	32,195	47,258	374,039	376,588
Common stock issued under employee benefit plans, net of restricted stock cancellations			$ 0	$ 0
Balance (in shares)	58,677,483	51,787,972	58,677,483	51,787,972
Balance, end of period, net of tax	$ 0	$ 0	$ 0	$ 0
Common Stock | Common Stock
Stockholders Equity Note [Line Items]
Issuance of stock (in shares)	2,227,000		4,527,000
Issuance of stock	$ 0		$ 0
Issuance of common stock for the acquisition of Boston Private (in shares)	1,887,981		1,887,981
Issuance of common stock for the acquisition of Boston Private	$ 0		$ 0
Additional Paid-in Capital
Stockholders Equity Note [Line Items]
Balance, beginning of period, net of tax	2,755	1,523	1,585	1,470
Common stock issued under employee benefit plans, net of restricted stock cancellations	2	4	(1)	18
Share-based compensation, net	38	22	93	61
Balance, end of period, net of tax	5,100	1,549	5,100	1,549
Additional Paid-in Capital | Common Stock
Stockholders Equity Note [Line Items]
Issuance of stock	1,245		2,363
Issuance of common stock for the acquisition of Boston Private	1,060		1,060
Retained Earnings
Stockholders Equity Note [Line Items]
Balance, beginning of period, net of tax	6,706	4,842	5,672	4,576
Net income	387	446	1,439	815
Dividends on preferred stock	(22)	(4)	40	(12)
Balance, end of period, net of tax	7,071	5,284	7,071	5,284
Accumulated Other Comprehensive Income
Stockholders Equity Note [Line Items]
Balance, beginning of period, net of tax	142	614	623	84
Other comprehensive income, net of tax		6
Balance, end of period, net of tax	65	620	65	620
Total SVBFG Stockholders’ Equity
Stockholders Equity Note [Line Items]
Balance, beginning of period, net of tax	11,667	7,319	8,220	6,470
Common stock issued under employee benefit plans, net of restricted stock cancellations	2	4	(1)	18
Net income	387	446	1,439	815
Other comprehensive income, net of tax	(77)	6
Share-based compensation, net	38	22	93	61
Dividends on preferred stock	(22)	(4)	(40)	(12)
Balance, end of period, net of tax	14,300	7,793	14,300	7,793
Total SVBFG Stockholders’ Equity | Common Stock
Stockholders Equity Note [Line Items]
Issuance of stock	1,245		2,363
Issuance of common stock for the acquisition of Boston Private	1,060		1,060
Total SVBFG Stockholders’ Equity | Noncumulative Preferred Stock
Stockholders Equity Note [Line Items]
Issuance of stock			1,724
Noncontrolling Interests
Stockholders Equity Note [Line Items]
Balance, beginning of period, net of tax	300	149	213	151
Net income	88	28	226	40
Capital calls and distributions, net	(19)	(3)	(70)	(17)
Balance, end of period, net of tax	$ 369	$ 174	$ 369	$ 174