Loans (Loans Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases receivable held to maturity	$ 7,410,881	$ 6,393,226
Unearned discount	(1,624)	(556)
Deferred loan fees	(1,560)	(1,206)
Total net loans receivable held to maturity	7,407,697	6,391,464
Allowance for loan losses	(61,963)	(55,686)
Loans receivable, net	7,345,734	6,335,778
Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases receivable held to maturity	5,731,712	4,809,875
Commercial \| Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases receivable held to maturity	2,020,231	1,646,606
Commercial \| Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases receivable held to maturity	3,711,481	3,163,269
Agricultural and agricultural real estate
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases receivable held to maturity	565,408	511,588
Residential real estate
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases receivable held to maturity	673,603	624,279
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases receivable held to maturity	$ 440,158	$ 447,484

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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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 and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums over and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans and leases covered under loss sharing agreements.

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