Loans and Allowance for Credit Losses - Total Acquired Credit Impaired Loans Outstanding by Portfolio Segment and Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	$ 10,089,117	$ 8,279,778
ACI
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	203,275	260,560
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	6,197,342	5,133,786
Commercial and Industrial | ACI
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	16,807	29,577
Commercial and Industrial | General C&I
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	3,275,362	2,746,454
Commercial and Industrial | General C&I | ACI
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	16,807	23,428
Commercial and Industrial | Healthcare
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	539,839	416,423
Commercial and Industrial | Healthcare | ACI
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable		6,149
Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	1,330,739	1,158,401
Commercial Real Estate | ACI
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	65,427	79,861
Commercial Real Estate | Income Producing
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	1,266,791	1,082,929
Commercial Real Estate | Income Producing | ACI
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	65,427	79,861
Consumer
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	2,294,753	1,765,736
Consumer | Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	2,227,653	1,690,814
Consumer | Other
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	67,100	74,922
Consumer | ACI
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	121,041	151,122
Consumer | ACI | Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	120,495	149,942
Consumer | ACI | Other
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	$ 546	$ 1,180