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		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 123,542	$ 112,205	$ 142,886	$ 110,651
Charge-offs	(6,382)	(15,375)	(27,532)	(21,001)
Recoveries	1,621	4,169	2,933	5,536
Provision for (Reduction of) Loan Losses	1,947	18,572	2,441	24,385
Ending Balance	120,728	119,571	120,728	119,571
Commercial loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	117,405	104,981	136,542	103,413
Charge-offs	(6,382)	(14,506)	(27,532)	(20,132)
Recoveries	1,520	4,102	2,726	5,089
Provision for (Reduction of) Loan Losses	1,841	18,190	2,648	24,397
Ending Balance	114,384	112,767	114,384	112,767
Consumer loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	6,137	7,224	6,344	7,238
Charge-offs	0	(869)	0	(869)
Recoveries	101	67	207	447
Provision for (Reduction of) Loan Losses	106	382	(207)	(12)
Ending Balance	6,344	6,804	6,344	6,804
Software
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	55,241	45,010	64,084	42,648
Charge-offs	(4,015)	(3,574)	(12,025)	(5,092)
Recoveries	119	397	233	639
Provision for (Reduction of) Loan Losses	1,894	4,965	947	8,603
Ending Balance	53,239	46,798	53,239	46,798
Hardware
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	25,236	27,869	36,553	29,761
Charge-offs	(412)	(4,434)	(12,587)	(6,431)
Recoveries	1,182	403	1,957	849
Provision for (Reduction of) Loan Losses	(1,226)	9,350	(1,143)	9,009
Ending Balance	24,780	33,188	24,780	33,188
Venture capital/private equity
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	17,676	10,482	16,385	9,963
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for (Reduction of) Loan Losses	1,328	3,111	2,619	3,630
Ending Balance	19,004	13,593	19,004	13,593
Life science
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	11,474	13,946	11,926	13,606
Charge-offs	(249)	(491)	(930)	(2,561)
Recoveries	190	886	288	1,089
Provision for (Reduction of) Loan Losses	(818)	(2,600)	(687)	(393)
Ending Balance	10,597	11,741	10,597	11,741
Premium wine
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,737	3,699	3,914	3,523
Charge-offs	0	0	0	0
Recoveries	19	41	238	131
Provision for (Reduction of) Loan Losses	(210)	53	(606)	139
Ending Balance	3,546	3,793	3,546	3,793
Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	4,041	3,975	3,680	3,912
Charge-offs	(1,706)	(6,007)	(1,990)	(6,048)
Recoveries	10	2,375	10	2,381
Provision for (Reduction of) Loan Losses	873	3,311	1,518	3,409
Ending Balance	$ 3,218	$ 3,654	$ 3,218	$ 3,654