Fair Value - Estimated fair value and related carrying amount, of the Company’s financial instruments - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financial assets:
Loans held for sale	$ 50,572	$ 41,649
Financial liabilities:
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	313,773	288,231
Increase (Decrease) in Loans Held-for-sale	690,495	318,936	$ 76,213
Other borrowings	55,358	55,158
Carrying Amount
Financial assets:
Cash and cash equivalents	374,448	695,794
Investment securities	1,014,981	1,027,748
Loans held for sale	50,572	41,649
Loans, net of allowance for loan losses	6,643,326	5,970,044
FDIC receivable for loss share agreements		4,401
Accrued interest receivable	18,618	17,083
Mortgage servicing rights	29,037	26,202
Other derivative financial instruments (Mortgage - banking related)	2,606	1,415
Financial liabilities:
Deposits	7,334,423	7,100,428
Federal funds purchased and securities sold under agreements to repurchase	313,773	288,231
Other borrowings	55,358	55,158
Accrued interest payable	1,359	2,190
Interest rate swap - cash flow hedge	498	718
Other derivative financial instruments (Mortgage banking related)	232	120
Fair Value.
Financial assets:
Cash and cash equivalents	374,448	695,794
Investment securities	1,015,137	1,028,157
Loans held for sale	50,572	41,649
Loans, net of allowance for loan losses	6,649,575	6,068,252
FDIC receivable for loss share agreements		(2,452)
Accrued interest receivable	18,618	17,083
Mortgage servicing rights	29,037	26,202
Other derivative financial instruments (Mortgage - banking related)	2,606	1,415
Financial liabilities:
Deposits	6,935,867	6,785,911
Federal funds purchased and securities sold under agreements to repurchase	313,773	288,231
Other borrowings	54,379	49,762
Accrued interest payable	1,359	2,190
Interest rate swap - cash flow hedge	498	718
Other derivative financial instruments (Mortgage banking related)	232	120
Commitments to extend credit | Fair Value.
Financial liabilities:
Off balance sheet financial instruments	1,587	23,927
Quoted Prices In Active Markets for Identical Assets (Level 1) | Fair Value.
Financial assets:
Cash and cash equivalents	374,448	695,794
Investment securities	12,041	11,489
Significant Other Observable Inputs (Level 2) | Fair Value.
Financial assets:
Investment securities	1,003,096	1,016,668
Loans held for sale	50,572	41,649
Accrued interest receivable	3,642	3,883
Other derivative financial instruments (Mortgage - banking related)	2,606	1,415
Financial liabilities:
Deposits	6,935,867	6,785,911
Federal funds purchased and securities sold under agreements to repurchase	313,773	288,231
Other borrowings	54,379	49,762
Accrued interest payable	1,359	2,190
Interest rate swap - cash flow hedge	498	718
Other derivative financial instruments (Mortgage banking related)	232	120
Significant Other Observable Inputs (Level 2) | Commitments to extend credit | Fair Value.
Financial liabilities:
Off balance sheet financial instruments	1,587	23,927
Significant Unobservable Inputs (Level 3) | Fair Value.
Financial assets:
Loans, net of allowance for loan losses	6,649,575	6,068,252
FDIC receivable for loss share agreements		(2,452)
Accrued interest receivable	14,976	13,200
Mortgage servicing rights	$ 29,037	$ 26,202