Schedule of Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Certain Loans and Debt Securities Acquired in Transfer, Allowance for Credit Losses Due to Subsequent Impairment			$ 565	$ 427
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 76,214	$ 76,817
Provision charged to operating expense	1,730	4,000
Less loans charged-off	(3,855)	(4,302)
Add back recoveries of loans previously charged-off	2,142	3,409
Ending balance	76,231	79,924
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans individually evaluated for impairment			15,465	13,954
Loans collectively evaluated for impairment			60,766	62,260
Ending balance	76,214	76,817	76,231	76,214
Total loans:
Individually evaluated for impairment			97,746	104,691
Individually evaluated for impairment			5,278,796	5,312,059
Total loans			5,376,542	5,416,750
Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	28,625	52,296
Provision charged to operating expense	4,387	(16,081)
Less loans charged-off	(444)	(1,922)
Add back recoveries of loans previously charged-off	524	2,359
Ending balance	33,092	36,652
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans individually evaluated for impairment			8,066	4,588
Loans collectively evaluated for impairment			25,026	24,037
Ending balance	28,625	52,296	33,092	28,625
Total loans:
Individually evaluated for impairment			63,512	68,632
Individually evaluated for impairment			3,393,354	3,445,451
Total loans			3,456,866	3,514,083
Total consumer loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	7,711	5,144
Provision charged to operating expense	2,048	1,229
Less loans charged-off	(2,596)	(1,892)
Add back recoveries of loans previously charged-off	1,205	775
Ending balance	8,368	5,256
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans individually evaluated for impairment			0	0
Loans collectively evaluated for impairment			8,368	7,711
Ending balance	7,711	5,144	8,368	7,711
Total loans:
Individually evaluated for impairment			0	0
Individually evaluated for impairment			973,161	970,266
Total loans			973,161	970,266
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	38,092	18,775
Provision charged to operating expense	(4,128)	17,690
Less loans charged-off	(793)	(488)
Add back recoveries of loans previously charged-off	391	275
Ending balance	33,562	36,252
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans individually evaluated for impairment			7,176	9,254
Loans collectively evaluated for impairment			26,386	28,838
Ending balance	38,092	18,775	33,562	38,092
Total loans:
Individually evaluated for impairment			33,079	32,397
Individually evaluated for impairment			784,762	765,545
Total loans			817,841	797,942
Agriculture
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,786	602
Provision charged to operating expense	(577)	1,162
Less loans charged-off	(22)	0
Add back recoveries of loans previously charged-off	22	0
Ending balance	1,209	1,764
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans individually evaluated for impairment			223	112
Loans collectively evaluated for impairment			986	1,674
Ending balance	1,786	602	1,209	1,786
Total loans:
Individually evaluated for impairment			1,155	3,662
Individually evaluated for impairment			124,337	129,196
Total loans			125,492	132,858
Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0	0
Provision charged to operating expense	0	0
Less loans charged-off	0	0
Add back recoveries of loans previously charged-off	0	0
Ending balance	0	0
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans individually evaluated for impairment			0	0
Loans collectively evaluated for impairment			0	0
Ending balance	$ 0	$ 0	0	0
Total loans:
Individually evaluated for impairment			0	0
Individually evaluated for impairment			3,182	1,601
Total loans			$ 3,182	$ 1,601

Loans And Leases Receivable Held For Investment, Evaluated for Impairment

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