Loans and Allowance for Loan Losses - Activity in Allowance for Loan Losses Broken out by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 120,728	$ 119,571	$ 142,886	$ 110,651
Charge-offs	(10,657)	(8,149)	(38,189)	(29,150)
Recoveries	2,380	2,674	5,313	8,210
Provision for (Reduction of) Loan Losses	16,610	10,638	19,051	35,023
Ending Balance	129,061	124,734	129,061	124,734
Software
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	53,239	46,798	64,084	42,648
Charge-offs	(6,907)	(2,527)	(18,932)	(7,619)
Recoveries	790	816	1,023	1,455
Provision for (Reduction of) Loan Losses	11,078	4,369	12,025	12,972
Ending Balance	58,200	49,456	58,200	49,456
Hardware
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	24,780	33,188	36,553	29,761
Charge-offs	(2,643)	(5,544)	(15,230)	(11,975)
Recoveries	113	1,149	2,070	1,998
Provision for (Reduction of) Loan Losses	2,491	7,370	1,348	16,379
Ending Balance	24,741	36,163	24,741	36,163
Venture capital/private equity
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	19,004	13,593	16,385	9,963
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for (Reduction of) Loan Losses	845	617	3,464	4,247
Ending Balance	19,849	14,210	19,849	14,210
Life science
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	10,597	11,741	11,926	13,606
Charge-offs	0	(57)	(930)	(2,618)
Recoveries	53	246	341	1,335
Provision for (Reduction of) Loan Losses	1,591	(780)	904	(1,173)
Ending Balance	12,241	11,150	12,241	11,150
Premium wine
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,546	3,793	3,914	3,523
Charge-offs	(35)	0	(35)	0
Recoveries	0	4	238	135
Provision for (Reduction of) Loan Losses	710	81	104	220
Ending Balance	4,221	3,878	4,221	3,878
Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,218	3,654	3,680	3,912
Charge-offs	(1,072)	(21)	(3,062)	(6,069)
Recoveries	1,306	77	1,316	2,458
Provision for (Reduction of) Loan Losses	(530)	(24)	988	3,385
Ending Balance	2,922	3,686	2,922	3,686
Commercial loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	114,384	112,767	136,542	103,413
Charge-offs	(10,657)	(8,149)	(38,189)	(28,281)
Recoveries	2,262	2,292	4,988	7,381
Provision for (Reduction of) Loan Losses	16,185	11,633	18,833	36,030
Ending Balance	122,174	118,543	122,174	118,543
Consumer loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	6,344	6,804	6,344	7,238
Charge-offs	0	0	0	(869)
Recoveries	118	382	325	829
Provision for (Reduction of) Loan Losses	425	(995)	218	(1,007)
Ending Balance	$ 6,887	$ 6,191	$ 6,887	$ 6,191