Segment Reporting Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Segment Reporting Information [Line Items]
Net interest income	$ 393,706	$ 373,974	$ 342,696	$ 309,993	$ 296,605	$ 289,161	$ 283,336	$ 281,421	$ 1,420,369	$ 1,150,523		$ 1,006,425
Provision for Loan and Lease Losses	22,242	23,522	15,806	30,734	16,454	20,004	36,746	33,475	92,304	106,679	[1]	95,683	[1]
Noninterest Income	152,266	158,778	128,528	117,659	113,502	144,140	112,776	86,134	557,231	456,552		472,794
Noninterest expense	$ (264,015)	$ (257,761)	$ (251,246)	$ (237,633)	$ (235,186)	$ (220,773)	$ (199,939)	$ (203,899)	(1,010,655)	(859,797)	[1]	(779,962)	[1]
Income before income tax expense									874,641	640,599		603,574
Total average loans, net of unearned income									21,159,394	18,283,591		14,762,941
Total average assets									48,380,272	43,987,451		40,846,377
Total average deposits									42,745,148	38,759,059		36,293,362
Global Commercial Bank
Segment Reporting Information [Line Items]
Net interest income									1,274,366	1,040,712		853,882
Provision for Loan and Lease Losses									81,553	93,885		94,913
Noninterest Income									366,000	320,421		272,862
Noninterest expense									(706,341)	(632,264)		(578,888)
Income before income tax expense									852,472	634,984		452,943
Total average loans, net of unearned income									18,479,793	16,047,545		12,984,646
Total average assets									46,303,582	41,494,321		38,438,858
Total average deposits									41,043,731	37,301,483		34,996,194
SVB Private Bank
Segment Reporting Information [Line Items]
Net interest income									58,131	53,582		44,412
Provision for Loan and Lease Losses									4,386	1,812		2,716
Noninterest Income									2,175	2,713		2,011
Noninterest expense									(17,693)	(12,379)		(12,185)
Income before income tax expense									38,227	42,104		31,522
Total average loans, net of unearned income									2,423,078	2,025,381		1,592,065
Total average assets									2,449,763	2,047,513		1,457,461
Total average deposits									1,303,542	1,133,425		1,108,411
SVB Capital
Segment Reporting Information [Line Items]
Net interest income									48	(49)		3
Provision for Loan and Lease Losses									0	0		0
Noninterest Income									58,992	49,365		70,857
Noninterest expense									(19,340)	(15,546)		(14,699)
Income before income tax expense									39,700	33,770		56,161
Total average loans, net of unearned income									0	0		0
Total average assets									325,939	338,848		337,884
Total average deposits									0	0		0
Other Items
Segment Reporting Information [Line Items]
Net interest income									87,824	56,278		108,128
Provision for Loan and Lease Losses									6,365	10,982		(1,946)
Noninterest Income									130,064	84,053		127,064
Noninterest expense									(267,281)	(199,608)		(174,190)
Income before income tax expense									(55,758)	(70,259)		62,948
Total average loans, net of unearned income									256,523	210,665		186,230
Total average assets									(699,012)	106,769		612,174
Total average deposits									$ 397,875	$ 324,151		$ 188,757

[1] Our consolidated statements of income for the years ended December 31, 2016 and 2015 were modified from prior periods’ 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 separately as a component of noninterest expense.