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
	Mar. 31, 2014	Mar. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 142,886	$ 110,651
Charge-offs	(21,150)	(5,626)
Recoveries	1,312	1,367
Provision for (Reduction of) Loan Losses	494	5,813
Ending Balance	123,542	112,205
Commercial loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	136,542	103,413
Charge-offs	(21,150)	(5,626)
Recoveries	1,206	987
Provision for (Reduction of) Loan Losses	807	6,207
Ending Balance	117,405	104,981
Consumer loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	6,344	7,238
Charge-offs	0	0
Recoveries	106	380
Provision for (Reduction of) Loan Losses	(313)	(394)
Ending Balance	6,137	7,224
Software
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	64,084	42,648
Charge-offs	(8,010)	(1,518)
Recoveries	114	242
Provision for (Reduction of) Loan Losses	(947)	3,638
Ending Balance	55,241	45,010
Hardware
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	36,553	29,761
Charge-offs	(12,175)	(1,997)
Recoveries	775	446
Provision for (Reduction of) Loan Losses	83	(341)
Ending Balance	25,236	27,869
Venture capital/private equity
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	16,385	9,963
Charge-offs	0	0
Recoveries	0	0
Provision for (Reduction of) Loan Losses	1,291	519
Ending Balance	17,676	10,482
Life science
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	11,926	13,606
Charge-offs	(681)	(2,070)
Recoveries	98	203
Provision for (Reduction of) Loan Losses	131	2,207
Ending Balance	11,474	13,946
Premium wine
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,914	3,523
Charge-offs	0	0
Recoveries	219	90
Provision for (Reduction of) Loan Losses	(396)	86
Ending Balance	3,737	3,699
Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,680	3,912
Charge-offs	(284)	(41)
Recoveries	0	6
Provision for (Reduction of) Loan Losses	645	98
Ending Balance	$ 4,041	$ 3,975