Activity in Allowance for Loan Losses Broken out by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	$ 89,947	$ 82,627
Charge-offs	(33,319)	(23,904)
Recoveries	9,693	25,123
Provision for (Reduction of)	44,330	6,101	44,628
Ending Balance	110,651	89,947	82,627
Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	82,366	72,104
Charge-offs	(32,712)	(23,684)
Recoveries	8,342	20,452
Provision for (Reduction of)	45,417	13,494
Ending Balance	103,413	82,366
Commercial loans | Software
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	38,263	29,288
Charge-offs	(4,316)	(10,252)
Recoveries	4,874	11,659
Provision for (Reduction of)	3,827	7,568
Ending Balance	42,648	38,263
Commercial loans | Hardware
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	16,810	14,688
Charge-offs	(20,247)	(4,828)
Recoveries	1,107	455
Provision for (Reduction of)	32,091	6,495
Ending Balance	29,761	16,810
Commercial loans | Venture capital/private equity
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	7,319	8,241
Charge-offs	0	0
Recoveries	0	0
Provision for (Reduction of)	2,644	(922)
Ending Balance	9,963	7,319
Commercial loans | Life science
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	10,243	9,077
Charge-offs	(5,080)	(4,201)
Recoveries	334	6,644
Provision for (Reduction of)	8,109	(1,277)
Ending Balance	13,606	10,243
Commercial loans | Premium wine
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	3,914	5,492
Charge-offs	(584)	(449)
Recoveries	650	1,223
Provision for (Reduction of)	(457)	(2,352)
Ending Balance	3,523	3,914
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	5,817	5,318
Charge-offs	(2,485)	(3,954)
Recoveries	1,377	471
Provision for (Reduction of)	(797)	3,982
Ending Balance	3,912	5,817
Consumer loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	7,581	10,523
Charge-offs	(607)	(220)
Recoveries	1,351	4,671
Provision for (Reduction of)	(1,087)	(7,393)
Ending Balance	$ 7,238	$ 7,581