Loans (Impaired loans not covered by loss share agreements) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
Unpaid Contractual Balance
Total impaired loans with a related allowance	$ 30,013	$ 30,013	$ 9,210
Total impaired loans without a related allowance	85,593	85,593	74,644
Total impaired loans held to maturity	115,606	115,606	83,854
Loan Balance
Total impaired loans with a related allowance	29,514	29,514	9,093
Total impaired loans without a related allowance	80,843	80,843	71,128
Total impaired loans held to maturity	110,357	110,357	80,221
Related Allowance Recorded	7,542	7,542	2,768
Average Loan Balance
Total impaired loans with a related allowance	26,729	18,606	11,287
Total impaired loans without a related allowance	78,023	81,285	60,831
Total impaired loans held to maturity	104,752	99,891	72,118
Interest Income Recognized
Total impaired loans with a related allowance	229	477	80
Total impaired loans without a related allowance	701	1,942	2,268
Total impaired loans held to maturity	930	2,419	2,348
Commercial
Unpaid Contractual Balance
Total impaired loans with a related allowance	20,043	20,043	3,889
Total impaired loans without a related allowance	49,382	49,382	51,883
Total impaired loans held to maturity	69,425	69,425	55,772
Loan Balance
Total impaired loans with a related allowance	19,629	19,629	3,857
Total impaired loans without a related allowance	45,267	45,267	48,504
Total impaired loans held to maturity	64,896	64,896	52,361
Related Allowance Recorded	4,738	4,738	1,169
Average Loan Balance
Total impaired loans with a related allowance	18,817	11,680	3,063
Total impaired loans without a related allowance	41,656	48,750	45,955
Total impaired loans held to maturity	60,473	60,430	49,018
Interest Income Recognized
Total impaired loans with a related allowance	211	437	31
Total impaired loans without a related allowance	530	1,575	1,910
Total impaired loans held to maturity	741	2,012	1,941
Commercial | Commercial
Unpaid Contractual Balance
Total impaired loans with a related allowance	4,664	4,664	1,192
Total impaired loans without a related allowance	4,632	4,632	5,784
Total impaired loans held to maturity	9,296	9,296	6,976
Loan Balance
Total impaired loans with a related allowance	4,283	4,283	1,160
Total impaired loans without a related allowance	3,719	3,719	5,759
Total impaired loans held to maturity	8,002	8,002	6,919
Related Allowance Recorded	2,077	2,077	471
Average Loan Balance
Total impaired loans with a related allowance	3,121	2,566	524
Total impaired loans without a related allowance	4,413	7,105	7,511
Total impaired loans held to maturity	7,534	9,671	8,035
Interest Income Recognized
Total impaired loans with a related allowance	73	87	12
Total impaired loans without a related allowance	78	339	515
Total impaired loans held to maturity	151	426	527
Commercial | Commercial real estate
Unpaid Contractual Balance
Total impaired loans with a related allowance	15,379	15,379	2,697
Total impaired loans without a related allowance	44,750	44,750	46,099
Total impaired loans held to maturity	60,129	60,129	48,796
Loan Balance
Total impaired loans with a related allowance	15,346	15,346	2,697
Total impaired loans without a related allowance	41,548	41,548	42,745
Total impaired loans held to maturity	56,894	56,894	45,442
Related Allowance Recorded	2,661	2,661	698
Average Loan Balance
Total impaired loans with a related allowance	15,696	9,114	2,539
Total impaired loans without a related allowance	37,243	41,645	38,444
Total impaired loans held to maturity	52,939	50,759	40,983
Interest Income Recognized
Total impaired loans with a related allowance	138	350	19
Total impaired loans without a related allowance	452	1,236	1,395
Total impaired loans held to maturity	590	1,586	1,414
Agricultural and agricultural real estate
Unpaid Contractual Balance
Total impaired loans with a related allowance	3,181	3,181	0
Total impaired loans without a related allowance	13,974	13,974	4,612
Total impaired loans held to maturity	17,155	17,155	4,612
Loan Balance
Total impaired loans with a related allowance	3,181	3,181	0
Total impaired loans without a related allowance	13,974	13,974	4,612
Total impaired loans held to maturity	17,155	17,155	4,612
Related Allowance Recorded	967	967	0
Average Loan Balance
Total impaired loans with a related allowance	1,112	390	2,823
Total impaired loans without a related allowance	15,310	12,232	2,287
Total impaired loans held to maturity	16,422	12,622	5,110
Interest Income Recognized
Total impaired loans with a related allowance	0	0	0
Total impaired loans without a related allowance	23	118	175
Total impaired loans held to maturity	23	118	175
Residential real estate
Unpaid Contractual Balance
Total impaired loans with a related allowance	3,512	3,512	2,210
Total impaired loans without a related allowance	19,496	19,496	15,802
Total impaired loans held to maturity	23,008	23,008	18,012
Loan Balance
Total impaired loans with a related allowance	3,427	3,427	2,125
Total impaired loans without a related allowance	19,021	19,021	15,665
Total impaired loans held to maturity	22,448	22,448	17,790
Related Allowance Recorded	473	473	393
Average Loan Balance
Total impaired loans with a related allowance	3,602	3,285	2,524
Total impaired loans without a related allowance	18,660	17,684	10,186
Total impaired loans held to maturity	22,262	20,969	12,710
Interest Income Recognized
Total impaired loans with a related allowance	8	15	16
Total impaired loans without a related allowance	136	217	145
Total impaired loans held to maturity	144	232	161
Consumer
Unpaid Contractual Balance
Total impaired loans with a related allowance	3,277	3,277	3,111
Total impaired loans without a related allowance	2,741	2,741	2,347
Total impaired loans held to maturity	6,018	6,018	5,458
Loan Balance
Total impaired loans with a related allowance	3,277	3,277	3,111
Total impaired loans without a related allowance	2,581	2,581	2,347
Total impaired loans held to maturity	5,858	5,858	5,458
Related Allowance Recorded	1,364	1,364	1,206
Average Loan Balance
Total impaired loans with a related allowance	3,198	3,251	2,877
Total impaired loans without a related allowance	2,397	2,619	2,403
Total impaired loans held to maturity	5,595	5,870	5,280
Interest Income Recognized
Total impaired loans with a related allowance	10	25	33
Total impaired loans without a related allowance	12	32	38
Total impaired loans held to maturity	$ 22	$ 57	$ 71