Loans and Allowance for Loan Losses - Aging of Gross Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	$ 40,064	$ 19,367
60 - 89 Days Past Due	5,151	12,572
Greater Than 90 Days Past Due	1,487	4,438
Total Past Due	46,702	36,377
Current	11,390,598	10,958,891
Loans Past Due 90 Days or More Still Accruing Interest	93	99
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	39,840	14,462
60 - 89 Days Past Due	1,428	5,529
Greater Than 90 Days Past Due	93	99
Total Past Due	41,361	20,090
Current	10,268,136	9,951,730
Loans Past Due 90 Days or More Still Accruing Interest	93	99
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	188	248
60 - 89 Days Past Due	1	0
Greater Than 90 Days Past Due	0	0
Total Past Due	189	248
Current	1,105,268	971,551
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	40,028	14,710
60 - 89 Days Past Due	1,429	5,529
Greater Than 90 Days Past Due	93	99
Total Past Due	41,550	20,338
Current	11,373,404	10,923,281
Loans Past Due 90 Days or More Still Accruing Interest	93	99
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	36	4,657
60 - 89 Days Past Due	3,722	7,043
Greater Than 90 Days Past Due	1,394	4,339
Total Past Due	5,152	16,039
Current	17,194	35,610
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	9,102	9,804
60 - 89 Days Past Due	610	1,291
Greater Than 90 Days Past Due	56	99
Total Past Due	9,768	11,194
Current	4,226,640	4,102,546
Loans Past Due 90 Days or More Still Accruing Interest	56	99
Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	9,047	2,679
60 - 89 Days Past Due	4	3,965
Greater Than 90 Days Past Due	37	0
Total Past Due	9,088	6,644
Current	1,140,049	1,198,169
Loans Past Due 90 Days or More Still Accruing Interest	37	0
Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	19,588	4
60 - 89 Days Past Due	1	0
Greater Than 90 Days Past Due	0	0
Total Past Due	19,589	4
Current	2,651,011	2,408,382
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	1,892	395
60 - 89 Days Past Due	786	131
Greater Than 90 Days Past Due	0	0
Total Past Due	2,678	526
Current	1,174,250	1,179,462
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	0	0
Current	722,742	665,755
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	211	1,580
60 - 89 Days Past Due	27	142
Greater Than 90 Days Past Due	0	0
Total Past Due	238	1,722
Current	353,444	397,416
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	167	240
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	167	240
Current	983,810	872,586
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	21	8
60 - 89 Days Past Due	1	0
Greater Than 90 Days Past Due	0	0
Total Past Due	22	8
Current	121,458	98,965
Loans Past Due 90 Days or More Still Accruing Interest	$ 0	$ 0