Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned income (Additional Information) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 28,850,445	$ 28,338,280
Credit card loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	375,000	335,000
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,478,075	3,363,803
Real estate secured loans | Construction loans, premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	96,000	99,000
Real estate secured loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,679,084	2,612,971
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,099,408	3,033,643
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,679,084	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	2,311,701	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	302,671	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	$ 64,712	$ 71,485