Loans and Allowance for Loan Losses - Activity in Allowance for Loan Losses Broken out by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				$ 217,613				$ 165,359	$ 217,613	$ 165,359	$ 142,886
Charge-offs									(96,857)	(50,968)	(43,168)
Recoveries									12,212	6,209	6,404
Provision for loan losses	$ 7,073	$ 18,950	$ 36,333	33,341	$ 31,261	$ 33,403	$ 26,513	6,452	95,697	97,629	59,486
Allowance for Loan and Lease Losses, Foreign Currency Translation									(3,299)	(616)	(249)
Ending Balance	225,366				217,613				225,366	217,613	165,359
Software and internet
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance								80,981		80,981	64,084
Charge-offs											(21,031)
Recoveries											1,425
Provision for loan losses											36,547
Ending Balance											80,981
Hardware
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance								25,860		25,860	36,553
Charge-offs											(15,265)
Recoveries											2,238
Provision for loan losses											2,417
Ending Balance											25,860
Private equity/venture capital
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance								27,997		27,997	16,385
Charge-offs											0
Recoveries											0
Provision for loan losses											11,632
Ending Balance											27,997
Life science/healthcare
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance								15,208		15,208	11,926
Charge-offs											(2,951)
Recoveries											374
Provision for loan losses											5,925
Ending Balance											15,208
Premium wine
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance								4,473		4,473	3,914
Charge-offs											(35)
Recoveries											240
Provision for loan losses											354
Ending Balance											4,473
Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance								3,253		3,253	3,680
Charge-offs											(3,886)
Recoveries											1,748
Provision for loan losses											1,760
Ending Balance											3,253
Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				207,445				157,772	207,445	157,772	136,542
Charge-offs									(96,755)	(50,672)	(43,168)
Recoveries									11,954	6,046	6,025
Provision for loan losses									93,885	94,913	58,635
Ending Balance	213,182				207,445				213,182	207,445	157,772
Commercial loans | Software and internet
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				103,045				80,981	103,045	80,981
Charge-offs									(68,784)	(33,246)
Recoveries									7,278	1,621
Provision for loan losses									58,350	53,696
Allowance for Loan and Lease Losses, Foreign Currency Translation									(2,501)	(7)	(44)
Ending Balance	97,388				103,045				97,388	103,045	80,981
Commercial loans | Hardware
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				23,085				25,860	23,085	25,860
Charge-offs									(13,233)	(5,145)
Recoveries									1,667	3,332
Provision for loan losses									20,851	(1,035)
Allowance for Loan and Lease Losses, Foreign Currency Translation									(1,204)	73	(83)
Ending Balance	31,166				23,085				31,166	23,085	25,860
Commercial loans | Private equity/venture capital
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				35,282				27,997	35,282	27,997
Charge-offs									0	0
Recoveries									0	0
Provision for loan losses									15,114	7,391
Allowance for Loan and Lease Losses, Foreign Currency Translation									(97)	(106)	(20)
Ending Balance	50,299				35,282				50,299	35,282	27,997
Commercial loans | Life science/healthcare
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				36,576				15,208	36,576	15,208
Charge-offs									(9,693)	(7,291)
Recoveries									1,129	277
Provision for loan losses									(2,543)	28,400
Allowance for Loan and Lease Losses, Foreign Currency Translation									(23)	(18)	(66)
Ending Balance	25,446				36,576				25,446	36,576	15,208
Commercial loans | Premium wine
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				5,205				4,473	5,205	4,473
Charge-offs									0	0
Recoveries									0	7
Provision for loan losses									(1,260)	725
Allowance for Loan and Lease Losses, Foreign Currency Translation									170	0	0
Ending Balance	4,115				5,205				4,115	5,205	4,473
Commercial loans | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				4,252				3,253	4,252	3,253
Charge-offs									(5,045)	(4,990)
Recoveries									1,880	809
Provision for loan losses									3,373	5,736
Allowance for Loan and Lease Losses, Foreign Currency Translation									308	(556)	(49)
Ending Balance	4,768				4,252				4,768	4,252	3,253
Commercial loans | Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Foreign Currency Translation									(3,347)	(614)	(262)
Consumer loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				10,168				7,587	10,168	7,587	6,344
Charge-offs											0
Recoveries											379
Provision for loan losses											851
Ending Balance	$ 12,184				10,168				12,184	10,168	7,587
Consumer loans | Consumer Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				$ 10,168				$ 7,587	10,168	7,587
Charge-offs									(102)	(296)
Recoveries									258	163
Provision for loan losses									1,812	2,716
Allowance for Loan and Lease Losses, Foreign Currency Translation									$ 48	(2)	13
Ending Balance					$ 10,168					$ 10,168	$ 7,587