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, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 33,164,636	$ 28,338,280
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	29,387,950	25,304,637
Commercial loans | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	6,199,548	6,154,755
Commercial loans | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,371,159	1,234,557
Commercial loans | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	17,801,324	14,110,560
Commercial loans | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,368,048	2,385,612
Commercial loans | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,088,217	959,663
Commercial loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	559,654	459,490
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	3,776,686	3,033,643
Consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	489,949	420,672
Consumer loans | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 3,286,737	$ 2,612,971