Loans and Allowance for Credit Losses - Major classifications of loans (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Classifications of loans
Total loans	$ 6,286,527	$ 5,995,441
Less allowance for loan losses	(64,253)	(68,448)
Loans, net	6,222,274	5,926,993
Loans Receivable
Classifications of loans
Total loans	6,286,527	5,995,441
Less allowance for loan losses	(64,253)	(68,448)
Loans, net	6,222,274	5,926,993
Loans Receivable \| Home equity lines of credit
Classifications of loans
Total loans	622,804	597,806
Loans Receivable \| Indirect auto
Classifications of loans
Total loans	475,138	455,971
Loans Receivable \| Commercial
Classifications of loans
Total loans	3,678,174	3,445,190
Loans Receivable \| Commercial \| Owner occupied commercial real estate
Classifications of loans
Total loans	1,450,075	1,493,966
Loans Receivable \| Commercial \| Income producing commercial real estate
Classifications of loans
Total loans	918,963	823,729
Loans Receivable \| Commercial \| Construction
Classifications of loans
Total loans	383,558	342,078
Loans Receivable \| Commercial \| Commercial & industrial
Classifications of loans
Total loans	925,578	785,417
Loans Receivable \| Residential \| Residential mortgage
Classifications of loans
Total loans	1,035,467	1,029,663
Loans Receivable \| Residential \| Construction
Classifications of loans
Total loans	350,877	351,700
Loans Receivable \| Consumer installment
Classifications of loans
Total loans	$ 124,067	$ 115,111

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 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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