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	Mar. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	$ 80,829	$ 19,367
60 - 89 Days Past Due	4,094	12,572
Greater Than 90 Days Past Due	2,386	4,438
Total Past Due	87,309	36,377
Current	10,833,173	10,958,891
Loans Past Due 90 Days or More Still Accruing Interest	99	99
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	68,045	14,462
60 - 89 Days Past Due	3,724	5,529
Greater Than 90 Days Past Due	99	99
Total Past Due	71,868	20,090
Current	9,806,167	9,951,730
Loans Past Due 90 Days or More Still Accruing Interest	99	99
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	6,194	248
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	6,194	248
Current	1,011,264	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	74,239	14,710
60 - 89 Days Past Due	3,724	5,529
Greater Than 90 Days Past Due	99	99
Total Past Due	78,062	20,338
Current	10,817,431	10,923,281
Loans Past Due 90 Days or More Still Accruing Interest	99	99
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	6,590	4,657
60 - 89 Days Past Due	370	7,043
Greater Than 90 Days Past Due	2,287	4,339
Total Past Due	9,247	16,039
Current	15,742	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	9,609	9,804
60 - 89 Days Past Due	2,925	1,291
Greater Than 90 Days Past Due	99	99
Total Past Due	12,633	11,194
Current	4,140,041	4,102,546
Loans Past Due 90 Days or More Still Accruing Interest	99	99
Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	2,007	2,679
60 - 89 Days Past Due	480	3,965
Greater Than 90 Days Past Due	0	0
Total Past Due	2,487	6,644
Current	1,193,977	1,198,169
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	47,711	4
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	47,711	4
Current	2,174,061	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	7,248	395
60 - 89 Days Past Due	203	131
Greater Than 90 Days Past Due	0	0
Total Past Due	7,451	526
Current	1,173,859	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	1,400	0
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	1,400	0
Current	700,970	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	70	1,580
60 - 89 Days Past Due	116	142
Greater Than 90 Days Past Due	0	0
Total Past Due	186	1,722
Current	423,259	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	6,165	240
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	6,165	240
Current	910,378	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	29	8
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	29	8
Current	100,886	98,965
Loans Past Due 90 Days or More Still Accruing Interest	$ 0	$ 0