Loans - Loan Portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 11,050,548	$ 10,437,812
Deferred loan fees included in total loans	5,887	4,986
Overdrawn demand deposits included in total loans	8,239	8,587
Commercial and industrial \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3,994,142	3,529,914
Commercial and industrial \| Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	432,220	430,886
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,462,978	4,553,618
Commercial real estate \| Office, retail, and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,782,757	1,979,820
Commercial real estate \| Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	698,611	675,463
Commercial real estate \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	632,779	539,820
Commercial real estate \| Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,348,831	1,358,515
Total corporate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	8,889,340	8,514,418
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,161,208	1,923,394
Consumer loans \| Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	853,887	827,055
Consumer loans \| 1-4 family mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	888,797	774,357
Consumer loans \| Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 418,524	$ 321,982

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Carrying value as of the balance sheet date of payments made in excess of existing cash balances, which will be honored by the bank but reflected as a loan to the entity. Overdrafts generally have a very short time frame for correction or repayment and are therefore more similar to short-term bank financing than trade financing.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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