Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned income (Additional Information) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 29,209,573	$ 28,338,280
Credit card loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	377,000	335,000
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,601,841	3,363,803
Real estate secured loans | Construction loans, premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	94,000	99,000
Real estate secured loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,808,707	2,612,971
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,272,561	3,033,643
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,808,707	2,612,971
Consumer loans | Real estate secured loans | Loans for personal residence
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,418,103	2,251,292
Consumer loans | Real estate secured loans | Loans to eligible employees
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	330,374	290,194
Consumer loans | Real estate secured loans | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 60,230	$ 71,485