Loans and Allowance for Loan Losses - Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	$ 48,825	$ 57,773
Financing Receivable, Individually Evaluated for Impairment	234,460	182,684
Collectively Evaluated for Impairment	176,541	159,840
Financing Receivable, Collectively Evaluated for Impairment	19,665,484	16,559,386
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	47,702	57,630
Financing Receivable, Individually Evaluated for Impairment	230,558	182,541
Collectively Evaluated for Impairment	165,480	149,815
Financing Receivable, Collectively Evaluated for Impairment	17,501,054	14,788,206
Commercial loans | Software and internet
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	28,245	34,098
Financing Receivable, Individually Evaluated for Impairment	122,748	100,866
Collectively Evaluated for Impairment	69,143	68,947
Financing Receivable, Collectively Evaluated for Impairment	5,504,283	5,337,049
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	9,995	3,160
Financing Receivable, Individually Evaluated for Impairment	65,395	27,736
Collectively Evaluated for Impairment	21,171	19,925
Financing Receivable, Collectively Evaluated for Impairment	1,115,003	1,043,792
Commercial loans | Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Financing Receivable, Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	50,299	35,282
Financing Receivable, Collectively Evaluated for Impairment	7,691,148	5,467,577
Commercial loans | Life science/healthcare
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	8,709	20,230
Financing Receivable, Individually Evaluated for Impairment	38,361	51,354
Collectively Evaluated for Impairment	16,737	16,346
Financing Receivable, Collectively Evaluated for Impairment	1,814,643	1,659,288
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	520	90
Financing Receivable, Individually Evaluated for Impairment	3,187	2,065
Collectively Evaluated for Impairment	3,595	5,115
Financing Receivable, Collectively Evaluated for Impairment	875,135	845,230
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	233	52
Financing Receivable, Individually Evaluated for Impairment	867	520
Collectively Evaluated for Impairment	4,535	4,200
Financing Receivable, Collectively Evaluated for Impairment	500,842	435,270
Consumer loans | Consumer Loan
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	1,123	143
Financing Receivable, Individually Evaluated for Impairment	3,902	143
Collectively Evaluated for Impairment	11,061	10,025
Financing Receivable, Collectively Evaluated for Impairment	$ 2,164,430	$ 1,771,180