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, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	$ 100,922	$ 82,051	$ 89,947	$ 82,627
Charge-offs	(14,130)	(4,293)	(21,120)	(8,615)
Recoveries	3,375	4,263	6,811	11,056
Provision for (Reduction of)	7,999	134	22,528	(2,913)
Ending Balance	98,166	82,155	98,166	82,155
Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	91,819	72,785	82,366	72,104
Charge-offs	(13,523)	(4,293)	(20,513)	(8,615)
Recoveries	3,044	4,103	6,251	10,497
Provision for (Reduction of)	8,923	730	22,159	(661)
Ending Balance	90,263	73,325	90,263	73,325
Commercial loans | Software
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	35,425	30,479	38,263	29,288
Charge-offs	(2,118)	(518)	(2,977)	(1,622)
Recoveries	1,329	2,639	4,088	7,920
Provision for (Reduction of)	3,345	(727)	(1,393)	(3,713)
Ending Balance	37,981	31,873	37,981	31,873
Commercial loans | Hardware
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	30,348	15,840	16,810	14,688
Charge-offs	(10,413)		(14,261)	(15)
Recoveries	329	32	434	312
Provision for (Reduction of)	2,368	170	19,649	1,057
Ending Balance	22,632	16,042	22,632	16,042
Commercial loans | Venture capital/private equity
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	7,214	7,432	7,319	8,241
Provision for (Reduction of)	2,438	875	2,333	66
Ending Balance	9,652	8,307	9,652	8,307
Commercial loans | Life science
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	10,292	8,097	10,243	9,077
Charge-offs	(122)	(471)	(235)	(3,662)
Recoveries	92	505	313	1,128
Provision for (Reduction of)	1,398	(906)	1,339	682
Ending Balance	11,660	7,225	11,660	7,225
Commercial loans | Premium wine
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	3,738	4,504	3,914	5,492
Charge-offs	(584)	(449)	(584)	(449)
Recoveries	187	590	265	730
Provision for (Reduction of)	55	(636)	(199)	(1,764)
Ending Balance	3,396	4,009	3,396	4,009
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	4,802	6,433	5,817	5,318
Charge-offs	(286)	(2,855)	(2,456)	(2,867)
Recoveries	1,107	337	1,151	407
Provision for (Reduction of)	(681)	1,954	430	3,011
Ending Balance	4,942	5,869	4,942	5,869
Consumer loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	9,103	9,266	7,581	10,523
Charge-offs	(607)		(607)
Recoveries	331	160	560	559
Provision for (Reduction of)	(924)	(596)	369	(2,252)
Ending Balance	$ 7,903	$ 8,830	$ 7,903	$ 8,830