Loans and Allowance - Composition of Impaired Loans by Loan Class (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	$ 132,764		$ 132,764		$ 189,779
Impaired loans with related allowance - Unpaid Principal Balance	21,291		21,291		6,121
Unpaid Principal Balance	154,055		154,055		195,900
Impaired loans with no related allowance - Recorded Investment	85,024		85,024		114,253
Impaired loans with related allowance - Recorded Investment	18,393		18,393		5,502
Recorded Investment	103,417		103,417		119,755
Impaired financing receivable, allowance	3,370	1,475	3,370	1,475	1,583
Impaired loans with no related allowance - Average Recorded Investment	85,949	49,875	87,722	52,494
Impaired loans with related allowance - Average Recorded Investment	18,403	6,681	18,497	6,811
Average Recorded Investment	104,352	56,556	106,219	59,305
Impaired loans with no related allowance - Interest Income Recognized	1,133	841	3,350	2,026
Impaired loans with related allowance - Interest Income Recognized	10	5	53	12
Interest Income Recognized	1,143	846	3,403	2,038
Commercial and industrial loans
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	30,525		30,525		35,066
Impaired loans with related allowance - Unpaid Principal Balance	2,027		2,027		1,390
Impaired loans with no related allowance - Recorded Investment	13,122		13,122		16,371
Impaired loans with related allowance - Recorded Investment	1,810		1,810		1,216
Impaired financing receivable, allowance	773		773		683
Impaired loans with no related allowance - Average Recorded Investment	13,406	8,352	13,820	9,553
Impaired loans with related allowance - Average Recorded Investment	1,814	865	1,864	889
Impaired loans with no related allowance - Interest Income Recognized	86	110	263	184
Impaired loans with related allowance - Interest Income Recognized	10		30	7
Agricultural production financing and other loans to farmers
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	28		28		32
Impaired loans with related allowance - Unpaid Principal Balance	10,645		10,645
Impaired loans with no related allowance - Recorded Investment	25		25		30
Impaired loans with related allowance - Recorded Investment	10,645		10,645
Impaired financing receivable, allowance	1,100		1,100
Impaired loans with no related allowance - Average Recorded Investment	25	32	27	33
Impaired loans with related allowance - Average Recorded Investment	10,645		10,645
Real estate loans - Construction
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	11,455		11,455		16,109
Impaired loans with no related allowance - Recorded Investment	8,168		8,168		10,625
Impaired loans with no related allowance - Average Recorded Investment	8,026	4,115	8,197	4,262
Impaired loans with no related allowance - Interest Income Recognized	112	29	331	85
Real estate loans - Commercial and farm land
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	82,625		82,625		128,073
Impaired loans with related allowance - Unpaid Principal Balance	7,159		7,159		4,657
Impaired loans with no related allowance - Recorded Investment	60,605		60,605		83,033
Impaired loans with related allowance - Recorded Investment	4,478		4,478		4,215
Impaired financing receivable, allowance	1,013		1,013		894
Impaired loans with no related allowance - Average Recorded Investment	61,356	34,298	62,367	35,198
Impaired loans with related allowance - Average Recorded Investment	4,484	5,742	4,528	5,844
Impaired loans with no related allowance - Interest Income Recognized	895	620	2,663	1,642
Impaired loans with related allowance - Interest Income Recognized		5	23	5
Real estate loans - Residential
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	4,826		4,826		6,746
Impaired loans with related allowance - Unpaid Principal Balance	1,460		1,460		74
Impaired loans with no related allowance - Recorded Investment	2,986		2,986		3,910
Impaired loans with related allowance - Recorded Investment	1,460		1,460		71
Impaired financing receivable, allowance	484		484		6
Impaired loans with no related allowance - Average Recorded Investment	3,018	2,687	3,164	3,028
Impaired loans with related allowance - Average Recorded Investment	1,460	74	1,460	78
Impaired loans with no related allowance - Interest Income Recognized	40	82	93	114
Impaired loans with related allowance - Interest Income Recognized
Real estate loans - Home equity
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	3,272		3,272		3,299
Impaired loans with no related allowance - Recorded Investment	118		118		112
Impaired loans with no related allowance - Average Recorded Investment	118	217	147	236
Other loans
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance - Unpaid Principal Balance	33		33		454
Impaired loans with no related allowance - Recorded Investment					172
Impaired loans with no related allowance - Average Recorded Investment		174		184
Impaired loans with no related allowance - Interest Income Recognized				$ 1

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

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