Activity in the Allowance for Loan Losses Broken out by Portfolio Segment (Detail) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	$ 82,155	$ 71,789	$ 82,627	$ 72,450
Charge-offs	(8,248)	(12,289)	(16,863)	(40,602)
Recoveries	10,570	3,898	21,626	13,397
Provision for (Reduction of)	769	10,971	(2,144)	29,124
Allowance for loan losses, ending balance	85,246	74,369	85,246	74,369
Software | Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	31,873		29,288
Charge-offs	(3,125)		(4,747)
Recoveries	2,718		10,638
Provision for (Reduction of)	4,899		1,186
Allowance for loan losses, ending balance	36,365		36,365
Hardware | Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	16,042		14,688
Charge-offs	(4,813)		(4,828)
Recoveries	44		356
Provision for (Reduction of)	2,304		3,361
Allowance for loan losses, ending balance	13,577		13,577
Venture capital/private equity | Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	8,307		8,241
Provision for (Reduction of)	(497)		(431)
Allowance for loan losses, ending balance	7,810		7,810
Life science | Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	7,225		9,077
Charge-offs	(310)		(3,972)
Recoveries	3,359		4,487
Provision for (Reduction of)	(2,110)		(1,428)
Allowance for loan losses, ending balance	8,164		8,164
Premium wine | Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	4,009		5,492
Charge-offs			(449)
Recoveries	360		1,090
Provision for (Reduction of)	(354)		(2,118)
Allowance for loan losses, ending balance	4,015		4,015
Other | Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	5,869		5,318
Charge-offs			(2,867)
Recoveries	64		471
Provision for (Reduction of)	(359)		2,652
Allowance for loan losses, ending balance	5,574		5,574
Commercial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	73,325		72,104
Charge-offs	(8,248)		(16,863)
Recoveries	6,545		17,042
Provision for (Reduction of)	3,883		3,222
Allowance for loan losses, ending balance	75,505		75,505
Consumer loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance	8,830		10,523
Recoveries	4,025		4,584
Provision for (Reduction of)	(3,114)		(5,366)
Allowance for loan losses, ending balance	$ 9,741		$ 9,741