Segment Reporting - Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 419,863	$ 309,993
Provision for credit losses	(26,996)	(29,679)
Provision for credit losses	27,972	30,734
Noninterest income	155,518	117,659
Noninterest expense	(265,417)	(237,633)
Income before income tax expense	281,992	159,285
Total average loans, net of unearned income	23,807,212	20,069,314
Total average assets	52,367,242	45,301,034
Total average deposits	46,106,081	39,958,535
Global Commercial Bank
Segment Reporting Information [Line Items]
Net interest income	369,867	275,878
Provision for credit losses	(25,274)	(28,889)
Noninterest income	99,346	79,519
Noninterest expense	(184,751)	(172,916)
Income before income tax expense	259,188	153,592
Total average loans, net of unearned income	20,679,202	17,647,055
Total average assets	49,953,950	42,888,126
Total average deposits	44,041,634	38,296,563
SVB Private Bank
Segment Reporting Information [Line Items]
Net interest income	16,247	13,610
Provision for credit losses	(1,722)	(790)
Noninterest income	507	718
Noninterest expense	(6,043)	(3,919)
Income before income tax expense	8,989	9,619
Total average loans, net of unearned income	2,666,658	2,245,317
Total average assets	2,590,476	2,272,825
Total average deposits	1,572,424	1,336,849
SVB Capital
Segment Reporting Information [Line Items]
Net interest income	7	10
Provision for credit losses	0	0
Noninterest income	28,910	16,775
Noninterest expense	(5,046)	(3,472)
Income before income tax expense	23,871	13,313
Total average loans, net of unearned income	0	0
Total average assets	373,322	372,876
Total average deposits	0	0
Other Items
Segment Reporting Information [Line Items]
Net interest income	33,742	20,495
Provision for credit losses	(976)	(1,055)
Noninterest income	26,755	20,647
Noninterest expense	(69,577)	(57,326)
Income before income tax expense	(10,056)	(17,239)
Total average loans, net of unearned income	461,352	176,942
Total average assets	(550,506)	(232,793)
Total average deposits	$ 492,023	$ 325,123