Loans - (Credit Exposure for Loans as Determined by Company's Internal Risk Rating System) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Loans [Line Items]
Total Loans	$ 3,702,334	$ 3,178,947	$ 2,953,655
Commercial Loan [Member]
Loans [Line Items]
Total Loans	2,105,899	1,874,605
Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	859,155	716,237
Consumer [Member]
Loans [Line Items]
Total Loans	26,565	25,056
Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	710,715	563,049
Originated and acquired loans [Member]
Loans [Line Items]
Total Loans	3,590,025	3,058,324
Originated and acquired loans [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	2,081,197	1,845,130
Originated and acquired loans [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	847,155	703,478
Originated and acquired loans [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	26,235	24,575
Originated and acquired loans [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	635,438	485,141
ASC 310-30 [Member]
Loans [Line Items]
Total Loans	112,309	120,623	$ 140,064
ASC 310-30 [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	24,702	29,475
ASC 310-30 [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	12,000	12,759
ASC 310-30 [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	330	481
ASC 310-30 [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	75,277	77,908
Total Loans [Member]
Loans [Line Items]
Total Loans	3,702,334	3,178,947
Total Loans [Member] | Originated and acquired loans [Member]
Loans [Line Items]
Total Loans	3,590,025	3,058,324
Total Loans [Member] | Originated and acquired loans [Member] | Commercial and Industrial [Member]
Loans [Line Items]
Total Loans	1,495,088	1,376,022
Total Loans [Member] | Originated and acquired loans [Member] | Agriculture [Member]
Loans [Line Items]
Total Loans	161,649	138,895
Total Loans [Member] | Originated and acquired loans [Member] | Energy Loans [Member]
Loans [Line Items]
Total Loans	40,213	57,460
Total Loans [Member] | Originated and acquired loans [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	2,081,197	1,845,130
Total Loans [Member] | Originated and acquired loans [Member] | Total Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	635,438	485,141
Total Loans [Member] | Originated and acquired loans [Member] | Commercial Construction [Member]
Loans [Line Items]
Total Loans	112,086	107,681
Total Loans [Member] | Originated and acquired loans [Member] | Commercial Acquisition/Development [Member]
Loans [Line Items]
Total Loans	23,109	14,415
Total Loans [Member] | Originated and acquired loans [Member] | Multifamily [Member]
Loans [Line Items]
Total Loans	51,741	26,947
Total Loans [Member] | Originated and acquired loans [Member] | Owner-Occupied [Member]
Loans [Line Items]
Total Loans	384,247	272,753
Total Loans [Member] | Originated and acquired loans [Member] | Non Owner-Occupied [Member]
Loans [Line Items]
Total Loans	448,502	336,098
Total Loans [Member] | Originated and acquired loans [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	847,155	703,478
Total Loans [Member] | Originated and acquired loans [Member] | Senior lien
Loans [Line Items]
Total Loans	748,444	646,482
Total Loans [Member] | Originated and acquired loans [Member] | Junior lien
Loans [Line Items]
Total Loans	98,711	56,996
Total Loans [Member] | Originated and acquired loans [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	26,235	24,575
Total Loans [Member] | ASC 310-30 [Member]
Loans [Line Items]
Total Loans	112,309	120,623
Total Loans [Member] | ASC 310-30 [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	24,702	29,475
Total Loans [Member] | ASC 310-30 [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	12,000	12,759
Total Loans [Member] | ASC 310-30 [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	330	481
Total Loans [Member] | ASC 310-30 [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	75,277	77,908
Total Loans [Member] | Pass [Member]
Loans [Line Items]
Total Loans	3,555,116	3,059,969
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member]
Loans [Line Items]
Total Loans	3,477,582	2,975,079
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Commercial and Industrial [Member]
Loans [Line Items]
Total Loans	1,460,896	1,349,116
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Agriculture [Member]
Loans [Line Items]
Total Loans	156,059	118,068
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Energy Loans [Member]
Loans [Line Items]
Total Loans	39,290	55,814
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	2,004,778	1,773,222
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Total Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	613,168	479,959
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Commercial Construction [Member]
Loans [Line Items]
Total Loans	110,850	107,502
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Commercial Acquisition/Development [Member]
Loans [Line Items]
Total Loans	22,276	14,415
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Multifamily [Member]
Loans [Line Items]
Total Loans	49,605	24,817
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Owner-Occupied [Member]
Loans [Line Items]
Total Loans	348,533	250,224
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Non Owner-Occupied [Member]
Loans [Line Items]
Total Loans	430,437	333,225
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	833,439	697,466
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Senior lien
Loans [Line Items]
Total Loans	736,336	641,294
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Junior lien
Loans [Line Items]
Total Loans	97,103	56,172
Total Loans [Member] | Pass [Member] | Originated and acquired loans [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	26,197	24,432
Total Loans [Member] | Pass [Member] | ASC 310-30 [Member]
Loans [Line Items]
Total Loans	77,534	84,890
Total Loans [Member] | Pass [Member] | ASC 310-30 [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	19,846	23,954
Total Loans [Member] | Pass [Member] | ASC 310-30 [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	9,306	10,072
Total Loans [Member] | Pass [Member] | ASC 310-30 [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	208	327
Total Loans [Member] | Pass [Member] | ASC 310-30 [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	48,174	50,537
Total Loans [Member] | Special Mention [Member]
Loans [Line Items]
Total Loans	66,518	51,188
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member]
Loans [Line Items]
Total Loans	63,451	48,171
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Commercial and Industrial [Member]
Loans [Line Items]
Total Loans	13,070	10,829
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Agriculture [Member]
Loans [Line Items]
Total Loans	3,487	18,824
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	42,050	46,683
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Total Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	15,133	1,396
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Owner-Occupied [Member]
Loans [Line Items]
Total Loans	25,493	17,030
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Non Owner-Occupied [Member]
Loans [Line Items]
Total Loans	15,133	1,396
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	6,267	91
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Senior lien
Loans [Line Items]
Total Loans	5,720	91
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Junior lien
Loans [Line Items]
Total Loans	547
Total Loans [Member] | Special Mention [Member] | Originated and acquired loans [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	1	1
Total Loans [Member] | Special Mention [Member] | ASC 310-30 [Member]
Loans [Line Items]
Total Loans	3,067	3,017
Total Loans [Member] | Special Mention [Member] | ASC 310-30 [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	1,073	1,070
Total Loans [Member] | Special Mention [Member] | ASC 310-30 [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	1,074	1,055
Total Loans [Member] | Special Mention [Member] | ASC 310-30 [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	8	9
Total Loans [Member] | Special Mention [Member] | ASC 310-30 [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	912	883
Total Loans [Member] | Substandard [Member]
Loans [Line Items]
Total Loans	79,523	66,329
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member]
Loans [Line Items]
Total Loans	47,815	33,613
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Commercial and Industrial [Member]
Loans [Line Items]
Total Loans	20,219	14,824
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Agriculture [Member]
Loans [Line Items]
Total Loans	1,902	1,870
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Energy Loans [Member]
Loans [Line Items]
Total Loans	923	1,646
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	33,192	23,764
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Total Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	7,137	3,786
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Commercial Construction [Member]
Loans [Line Items]
Total Loans	1,236	179
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Commercial Acquisition/Development [Member]
Loans [Line Items]
Total Loans	833
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Multifamily [Member]
Loans [Line Items]
Total Loans	2,136	2,130
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Owner-Occupied [Member]
Loans [Line Items]
Total Loans	10,148	5,424
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Non Owner-Occupied [Member]
Loans [Line Items]
Total Loans	2,932	1,477
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	7,449	5,921
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Senior lien
Loans [Line Items]
Total Loans	6,388	5,097
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Junior lien
Loans [Line Items]
Total Loans	1,061	824
Total Loans [Member] | Substandard [Member] | Originated and acquired loans [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	37	142
Total Loans [Member] | Substandard [Member] | ASC 310-30 [Member]
Loans [Line Items]
Total Loans	31,708	32,716
Total Loans [Member] | Substandard [Member] | ASC 310-30 [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	3,783	4,451
Total Loans [Member] | Substandard [Member] | ASC 310-30 [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	1,620	1,632
Total Loans [Member] | Substandard [Member] | ASC 310-30 [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	114	145
Total Loans [Member] | Substandard [Member] | ASC 310-30 [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	26,191	26,488
Total Loans [Member] | Doubtful [Member]
Loans [Line Items]
Total Loans	1,177	1,461
Total Loans [Member] | Doubtful [Member] | Originated and acquired loans [Member]
Loans [Line Items]
Total Loans	1,177	1,461
Total Loans [Member] | Doubtful [Member] | Originated and acquired loans [Member] | Commercial and Industrial [Member]
Loans [Line Items]
Total Loans	903	1,253
Total Loans [Member] | Doubtful [Member] | Originated and acquired loans [Member] | Agriculture [Member]
Loans [Line Items]
Total Loans	201	133
Total Loans [Member] | Doubtful [Member] | Originated and acquired loans [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	1,177	1,461
Total Loans [Member] | Doubtful [Member] | Originated and acquired loans [Member] | Owner-Occupied [Member]
Loans [Line Items]
Total Loans	$ 73	$ 75