Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income, Broken Out by Portfolio Segment and Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 28,338,280	$ 23,106,316
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	3,033,643	2,629,486
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	25,304,637	20,476,830
Commercial loans | Software and internet
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	6,154,755	6,172,531
Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,234,557	1,193,599
Commercial loans | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	14,110,560	9,952,377
Commercial loans | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,385,612	1,808,827
Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	959,663	873,158
Commercial loans | Other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	459,490	476,338
Consumer loans | Other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	420,672	328,980
Consumer loans | Real estate secured consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 2,612,971	$ 2,300,506