Segment Reporting - Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Net interest income		$ 373,974	$ 289,161	$ 1,026,663	$ 853,918
Provision for credit losses		(22,409)	(18,950)	(67,273)	(88,624)
Provision for credit losses	[1]	23,522	20,004	70,062	90,225
Noninterest income		158,778	144,140	404,965	343,050
Noninterest expense	[1]	(257,761)	(220,773)	(746,640)	(624,611)
Income before income tax expense		251,469	192,524	614,926	482,132
Total average loans, net of unearned income		21,584,892	18,647,194	20,726,467	17,955,497
Total average assets		49,795,366	43,451,329	47,565,051	43,669,716
Total average deposits		44,042,842	37,909,754	42,061,635	38,443,990
Global Commercial Bank
Segment Reporting Information [Line Items]
Net interest income		337,860	262,484	924,789	773,342
Provision for credit losses		(20,874)	(16,974)	(65,007)	(86,143)
Noninterest income		97,227	79,226	260,650	231,295
Noninterest expense		(176,964)	(159,479)	(525,043)	(462,234)
Income before income tax expense		237,249	165,257	595,389	456,260
Total average loans, net of unearned income		18,807,616	16,357,099	18,125,020	15,769,964
Total average assets		47,817,114	40,828,549	45,414,432	41,020,808
Total average deposits		42,376,024	36,484,125	40,398,413	37,002,027
SVB Private Bank
Segment Reporting Information [Line Items]
Net interest income		14,600	13,298	42,952	40,508
Provision for credit losses		(1,535)	(1,976)	(2,266)	(2,481)
Noninterest income		460	664	1,715	2,052
Noninterest expense		(4,706)	(3,122)	(12,675)	(9,481)
Income before income tax expense		8,819	8,864	29,726	30,598
Total average loans, net of unearned income		2,499,507	2,074,982	2,371,027	1,978,175
Total average assets		2,538,400	2,096,237	2,403,777	1,999,455
Total average deposits		1,231,390	1,115,446	1,289,990	1,120,575
SVB Capital
Segment Reporting Information [Line Items]
Net interest income		15	1	41	(51)
Provision for credit losses		0	0	0	0
Noninterest income		13,913	30,619	45,707	44,492
Noninterest expense		(4,873)	(3,924)	(14,537)	(11,521)
Income before income tax expense		9,055	26,696	31,211	32,920
Total average loans, net of unearned income		0	0	0	0
Total average assets		323,417	325,321	333,439	334,328
Total average deposits		0	0	0	0
Other Items
Segment Reporting Information [Line Items]
Net interest income		21,499	13,378	58,881	40,119
Provision for credit losses		(1,113)	(1,054)	(2,789)	(1,601)
Noninterest income		47,178	33,631	96,893	65,211
Noninterest expense		(71,218)	(54,248)	(194,385)	(141,375)
Income before income tax expense		(3,654)	(8,293)	(41,400)	(37,646)
Total average loans, net of unearned income		277,769	215,113	230,420	207,358
Total average assets		(883,565)	201,222	(586,597)	315,125
Total average deposits		$ 435,428	$ 310,183	$ 373,232	$ 321,388

[1] Our consolidated statements of income for the three and nine months ended September 30, 2016 were modified from prior period's presentation to conform to the current period's presentation, which reflects our provision for loan losses and provision for unfunded credit commitments together as our “provision for credit losses”. In prior periods, our provision for unfunded credit commitments were reported as a component of noninterest expense.