Fair Value - Estimated fair value and related carrying amount, of the Company’s financial instruments - (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jan. 03, 2017	Dec. 31, 2016
Financial assets:
Loans held for sale	$ 65,995	$ 48,926		$ 50,572
Financial liabilities:
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	334,018	341,064	$ 1,014	313,773
Increase (Decrease) in Loans Held-for-sale	449,052	421,134
Other borrowings	98,147	55,254		55,358
Carrying Amount
Financial assets:
Cash and cash equivalents	431,890	481,912		374,448
Investment securities	1,358,894	1,007,060		1,014,981
Loans held for sale	65,995	48,926		50,572
Loans, net of allowance for loan losses	8,140,706	6,380,657		6,643,326
Interest Receivable	23,469	18,191		18,618
Mortgage servicing rights	29,930	22,350		29,037
Interest rate swap - non-designated hedge	208			203
Other derivative financial instruments (Mortgage - banking related)	1,748	3,257		2,403
Financial liabilities:
Deposits	9,031,654	7,163,926		7,334,423
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	334,018	341,064		313,773
Other borrowings	98,147	55,254		55,358
Interest Payable	1,502	1,649		1,359
Interest rate swap - non-designated hedge	203			181
Interest rate swap - cash flow hedge	389	776		498
Other derivative financial instruments (Mortgage banking related)		1,437		51
Fair Value.
Financial assets:
Cash and cash equivalents	431,890	481,912		374,448
Investment securities	1,358,976	1,007,370		1,015,137
Loans held for sale	65,995	48,926		50,572
Loans, net of allowance for loan losses	8,216,793	6,591,596		6,649,575
Interest Receivable	23,469	18,191		18,618
Mortgage servicing rights	29,930	22,350		29,037
Interest rate swap - non-designated hedge	208			203
Other derivative financial instruments (Mortgage - banking related)	1,748	3,257		2,403
Financial liabilities:
Deposits	8,481,700	6,980,410		6,935,867
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	334,018	341,064		313,773
Other borrowings	100,723	49,499		54,379
Interest Payable	1,502	1,649		1,359
Interest rate swap - non-designated hedge	203			181
Interest rate swap - cash flow hedge	389	776		498
Other derivative financial instruments (Mortgage banking related)		1,437		51
Commitments to extend credit | Fair Value.
Financial liabilities:
Commitments to extend credit	17,200			1,587
Standby letters of credit and financial guarantees | Fair Value.
Financial liabilities:
Commitments to extend credit		53,838
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	431,890	481,912		374,448
Investment securities	15,660	12,047		12,041
Significant Other Observable Inputs (Level 2)
Financial assets:
Investment securities	1,343,316	995,323		1,003,096
Loans held for sale	65,995	48,926		50,572
Interest Receivable	5,454	3,941		3,642
Interest rate swap - non-designated hedge	208			203
Other derivative financial instruments (Mortgage - banking related)	1,748	3,257		2,403
Financial liabilities:
Deposits	8,481,700	6,980,410		6,935,867
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	334,018	341,064		313,773
Other borrowings	100,723	49,499		54,379
Interest Payable	1,502	1,649		1,359
Interest rate swap - non-designated hedge	203			181
Interest rate swap - cash flow hedge	389	776		498
Other derivative financial instruments (Mortgage banking related)		1,437		51
Significant Other Observable Inputs (Level 2) | Commitments to extend credit
Financial liabilities:
Commitments to extend credit	17,200			1,587
Significant Other Observable Inputs (Level 2) | Standby letters of credit and financial guarantees
Financial liabilities:
Commitments to extend credit		53,838
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for loan losses	8,216,793	6,591,596		6,649,575
Interest Receivable	18,015	14,250		14,976
Mortgage servicing rights	29,930	22,350		29,037
Recurring basis
Financial assets:
Loans held for sale	65,995	48,926		50,572
Mortgage servicing rights	29,930	22,350		29,037
Recurring basis | Significant Other Observable Inputs (Level 2)
Financial assets:
Loans held for sale	65,995	48,926		50,572
Recurring basis | Significant Unobservable Inputs (Level 3)
Financial assets:
Mortgage servicing rights	$ 29,930	$ 22,350		$ 29,037