Segment Reporting - Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 493,222	$ 373,974	$ 1,379,528	$ 1,026,663
Provision for credit losses	(17,174)	(23,522)	(74,226)	(70,062)
Noninterest income	210,070	158,778	558,277	404,965
Noninterest expense	(309,445)	(257,761)	(880,601)	(746,640)
Income before income tax expense	376,673	251,469	982,978	614,926
Total average loans, net of unearned income	26,331,377	21,584,892	25,008,277	20,726,467
Total average assets	56,465,037	49,795,366	54,432,652	47,565,051
Total average deposits	49,092,240	44,042,842	47,734,362	42,061,635
Global Commercial Bank
Segment Reporting Information [Line Items]
Noninterest income	114,123		326,714
SVB Private Bank
Segment Reporting Information [Line Items]
Noninterest income	605		1,677
SVB Capital
Segment Reporting Information [Line Items]
Noninterest income	24,423		81,832
Operating segments | Global Commercial Bank
Segment Reporting Information [Line Items]
Net interest income	431,036	337,860	1,209,960	924,789
Provision for credit losses	(19,074)	(20,874)	(71,704)	(65,007)
Noninterest income	114,123	97,227	326,714	260,650
Noninterest expense	(206,487)	(178,306)	(591,434)	(528,807)
Income before income tax expense	319,598	235,907	873,536	591,625
Total average loans, net of unearned income	22,925,909	18,807,616	21,781,557	18,125,020
Total average assets	54,296,808	47,809,890	52,277,701	45,408,476
Total average deposits	47,037,693	42,376,024	45,701,317	40,398,413
Operating segments | SVB Private Bank
Segment Reporting Information [Line Items]
Net interest income	14,919	14,600	46,811	42,952
Provision for credit losses	(362)	(1,535)	(2,384)	(2,266)
Noninterest income	605	460	1,677	1,715
Noninterest expense	(6,760)	(4,706)	(18,729)	(12,675)
Income before income tax expense	8,402	8,819	27,375	29,726
Total average loans, net of unearned income	2,928,576	2,499,507	2,791,910	2,371,027
Total average assets	2,538,662	2,538,400	2,548,184	2,403,777
Total average deposits	1,505,746	1,231,390	1,519,200	1,289,990
Operating segments | SVB Capital
Segment Reporting Information [Line Items]
Net interest income	6	15	22	41
Provision for credit losses	0	0	0	0
Noninterest income	24,423	13,913	81,832	45,707
Noninterest expense	(6,469)	(4,873)	(17,182)	(14,537)
Income before income tax expense	17,960	9,055	64,672	31,211
Total average loans, net of unearned income	0	0	0	0
Total average assets	388,531	323,417	379,809	333,439
Total average deposits	0	0	0	0
Other Income
Segment Reporting Information [Line Items]
Net interest income	47,261	21,499	122,735	58,881
Provision for credit losses	2,262	(1,113)	(138)	(2,789)
Noninterest income	70,919	47,178	148,054	96,893
Noninterest expense	(89,729)	(69,876)	(253,256)	(190,621)
Income before income tax expense	30,713	(2,312)	17,395	(37,636)
Total average loans, net of unearned income	476,892	277,769	434,810	230,420
Total average assets	(758,964)	(876,341)	(773,042)	(580,641)
Total average deposits	$ 548,801	$ 435,428	$ 513,845	$ 373,232