Activity in Allowance for Loan Losses Broken out by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	$ 82,627	$ 72,450
Charge-offs	(23,904)	(51,239)
Recoveries	25,123	16,788
Provision for (Reduction of)	6,101	44,628
Ending Balance	89,947	82,627
Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	72,104	64,247
Charge-offs	(23,684)	(50,750)
Recoveries	20,452	16,250
Provision for (Reduction of)	13,494	42,357
Ending Balance	82,366	72,104
Commercial loans | Software
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	29,288	24,209
Charge-offs	(10,252)	(16,230)
Recoveries	11,659	5,838
Provision for (Reduction of)	7,568	15,471
Ending Balance	38,263	29,288
Commercial loans | Hardware
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	14,688	16,194
Charge-offs	(4,828)	(10,568)
Recoveries	455	5,715
Provision for (Reduction of)	6,495	3,347
Ending Balance	16,810	14,688
Commercial loans | Venture capital/private equity
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	8,241	5,664
Provision for (Reduction of)	(922)	2,577
Ending Balance	7,319	8,241
Commercial loans | Life science
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	9,077	9,651
Charge-offs	(4,201)	(17,629)
Recoveries	6,644	3,738
Provision for (Reduction of)	(1,277)	13,317
Ending Balance	10,243	9,077
Commercial loans | Premium wine
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	5,492	4,652
Charge-offs	(449)	(1,457)
Recoveries	1,223	222
Provision for (Reduction of)	(2,352)	2,075
Ending Balance	3,914	5,492
Commercial loans | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	5,318	3,877
Charge-offs	(3,954)	(4,866)
Recoveries	471	737
Provision for (Reduction of)	3,982	5,570
Ending Balance	5,817	5,318
Consumer loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	10,523	8,203
Charge-offs	(220)	(489)
Recoveries	4,671	538
Provision for (Reduction of)	(7,393)	2,271
Ending Balance	$ 7,581	$ 10,523