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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 119,571	$ 98,166	$ 110,651	$ 89,947
Charge-offs	(8,149)	(4,637)	(29,150)	(25,757)
Recoveries	2,674	1,207	8,210	8,018
Provision for (Reduction of) Loan Losses	10,638	6,788	35,023	29,316
Ending Balance	124,734	101,524	124,734	101,524
Commercial loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	112,767	90,263	103,413	82,366
Charge-offs	(8,149)	(4,637)	(28,281)	(25,150)
Recoveries	2,292	741	7,381	6,992
Provision for (Reduction of) Loan Losses	11,633	7,787	36,030	29,946
Ending Balance	118,543	94,154	118,543	94,154
Consumer loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	6,804	7,903	7,238	7,581
Charge-offs	0	0	(869)	(607)
Recoveries	382	466	829	1,026
Provision for (Reduction of) Loan Losses	(995)	(999)	(1,007)	(630)
Ending Balance	6,191	7,370	6,191	7,370
Software
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	46,798	37,981	42,648	38,263
Charge-offs	(2,527)	0	(7,619)	(2,977)
Recoveries	816	374	1,455	4,462
Provision for (Reduction of) Loan Losses	4,369	(1,110)	12,972	(2,503)
Ending Balance	49,456	37,245	49,456	37,245
Hardware
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	33,188	22,632	29,761	16,810
Charge-offs	(5,544)	(1,849)	(11,975)	(16,110)
Recoveries	1,149	106	1,998	540
Provision for (Reduction of) Loan Losses	7,370	6,796	16,379	26,445
Ending Balance	36,163	27,685	36,163	27,685
Venture capital/private equity
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	13,593	9,652	9,963	7,319
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for (Reduction of) Loan Losses	617	991	4,247	3,324
Ending Balance	14,210	10,643	14,210	10,643
Life science
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	11,741	11,660	13,606	10,243
Charge-offs	(57)	(2,781)	(2,618)	(3,016)
Recoveries	246	3	1,335	316
Provision for (Reduction of) Loan Losses	(780)	3,281	(1,173)	4,620
Ending Balance	11,150	12,163	11,150	12,163
Premium wine
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,793	3,396	3,523	3,914
Charge-offs	0	0	0	(584)
Recoveries	4	228	135	493
Provision for (Reduction of) Loan Losses	81	(463)	220	(662)
Ending Balance	3,878	3,161	3,878	3,161
Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,654	4,942	3,912	5,817
Charge-offs	(21)	(7)	(6,069)	(2,463)
Recoveries	77	30	2,458	1,181
Provision for (Reduction of) Loan Losses	(24)	(1,708)	3,385	(1,278)
Ending Balance	$ 3,686	$ 3,257	$ 3,686	$ 3,257