Loans, Allowance for Loan Losses, and Credit Quality - Summary of changes in ALLL by portfolio segment for periods - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Allowance for Loan Losses (ALLL):
Beginning balance	$ 13,153	$ 12,653	$ 12,653
Provision	900	1,360	1,600
Charge-offs	(629)	(1,110)	(1,213)
Recoveries	196	89	113
Net (charge-offs) recoveries	(433)	(1,021)	(1,100)
Ending balance	$ 13,620	12,992	$ 13,153
As percent of ALLL	100.00%		100.00%
ALLL:
Individually evaluated	$ 427		$ 0
Collectively evaluated	13,193		13,153
Loans:
Individually evaluated	12,738		9,939
Collectively evaluated	2,230,193		2,156,242
Total	2,242,931		2,166,181
Net loans	2,229,311		2,153,028
Retail & other
Allowance for Loan Losses (ALLL):
Beginning balance	304	225	225
Provision	225		267
Charge-offs	(251)		(204)
Recoveries	36		16
Net (charge-offs) recoveries	(215)		(188)
Ending balance	$ 314		$ 304
As percent of ALLL	2.00%		2.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	314		304
Loans:
Individually evaluated	12		12
Collectively evaluated	28,701		26,481
Total	28,713		26,493
Net loans	28,399		26,189
Commercial portfolio segment | Commercial & industrial
Allowance for Loan Losses (ALLL):
Beginning balance	5,271	4,934	4,934
Provision	356		1,107
Charge-offs	(59)		(813)
Recoveries	90		43
Net (charge-offs) recoveries	31		(770)
Ending balance	$ 5,658		$ 5,271
As percent of ALLL	42.00%		40.00%
ALLL:
Individually evaluated	$ 308		$ 0
Collectively evaluated	5,350		5,271
Loans:
Individually evaluated	2,143		2,927
Collectively evaluated	761,599		681,993
Total	763,742		684,920
Net loans	758,084		679,649
Commercial portfolio segment | Owner-occupied CRE
Allowance for Loan Losses (ALLL):
Beginning balance	2,847	2,607	2,607
Provision	(57)		300
Charge-offs	(13)		(74)
Recoveries	2		14
Net (charge-offs) recoveries	(11)		(60)
Ending balance	$ 2,779		$ 2,847
As percent of ALLL	20.00%		22.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	2,779		2,847
Loans:
Individually evaluated	2,552		1,506
Collectively evaluated	453,956		439,847
Total	456,508		441,353
Net loans	453,729		438,506
Commercial portfolio segment | AG production
Allowance for Loan Losses (ALLL):
Beginning balance	121	129	129
Provision	85		(8)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 206		$ 121
As percent of ALLL	1.00%		1.00%
ALLL:
Individually evaluated	$ 119		$ 0
Collectively evaluated	87		121
Loans:
Individually evaluated	1,251		0
Collectively evaluated	34,799		35,625
Total	36,050		35,625
Net loans	35,844		35,504
Commercial real estate portfolio segment | AG real estate
Allowance for Loan Losses (ALLL):
Beginning balance	301	296	296
Provision	46		5
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 347		$ 301
As percent of ALLL	3.00%		2.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	347		301
Loans:
Individually evaluated	1,089		222
Collectively evaluated	57,502		53,222
Total	58,591		53,444
Net loans	58,244		53,143
Commercial real estate portfolio segment | CRE investment
Allowance for Loan Losses (ALLL):
Beginning balance	1,470	1,388	1,388
Provision	32		119
Charge-offs	0		(37)
Recoveries	0		0
Net (charge-offs) recoveries	0		(37)
Ending balance	$ 1,502		$ 1,470
As percent of ALLL	11.00%		11.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	1,502		1,470
Loans:
Individually evaluated	2,483		1,686
Collectively evaluated	333,959		341,966
Total	336,442		343,652
Net loans	334,940		342,182
Commercial real estate portfolio segment | Construction & land development
Allowance for Loan Losses (ALLL):
Beginning balance	510	726	726
Provision	(140)		(216)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 370		$ 510
As percent of ALLL	3.00%		4.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	370		510
Loans:
Individually evaluated	427		603
Collectively evaluated	61,383		79,996
Total	61,810		80,599
Net loans	61,440		80,089
Residential | Residential first mortgage
Allowance for Loan Losses (ALLL):
Beginning balance	1,646	1,609	1,609
Provision	(75)		117
Charge-offs	0		(85)
Recoveries	36		5
Net (charge-offs) recoveries	36		(80)
Ending balance	$ 1,607		$ 1,646
As percent of ALLL	12.00%		12.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	1,607		1,646
Loans:
Individually evaluated	2,560		2,750
Collectively evaluated	340,840		355,091
Total	343,400		357,841
Net loans	341,793		356,195
Residential | Residential junior mortgage
Allowance for Loan Losses (ALLL):
Beginning balance	472	488	488
Provision	71		(51)
Charge-offs	(80)		0
Recoveries	32		35
Net (charge-offs) recoveries	(48)		35
Ending balance	$ 495		$ 472
As percent of ALLL	4.00%		4.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	495		472
Loans:
Individually evaluated	221		233
Collectively evaluated	115,958		111,095
Total	116,179		111,328
Net loans	115,684		110,856
Residential | Residential construction
Allowance for Loan Losses (ALLL):
Beginning balance	211	251	251
Provision	357		(40)
Charge-offs	(226)		0
Recoveries	0		0
Net (charge-offs) recoveries	(226)		0
Ending balance	$ 342		$ 211
As percent of ALLL	2.00%		2.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	342		211
Loans:
Individually evaluated	0		0
Collectively evaluated	41,496		30,926
Total	41,496		30,926
Net loans	41,154		30,715
Originated
Allowance for Loan Losses (ALLL):
Beginning balance	11,448	10,542	10,542
Provision	994		2,014
Charge-offs	(569)		(1,200)
Recoveries	191		92
Net (charge-offs) recoveries	(378)		(1,108)
Ending balance	$ 12,064		$ 11,448
As percent of ALLL	100.00%		100.00%
ALLL:
Individually evaluated	$ 427		$ 0
Collectively evaluated	11,637		11,448
Loans:
Individually evaluated	4,487		548
Collectively evaluated	1,646,206		1,484,617
Total	1,650,693		1,485,165
Net loans	1,638,629		1,473,717
Originated | Retail & other
Allowance for Loan Losses (ALLL):
Beginning balance	281	200	200
Provision	227		266
Charge-offs	(251)		(201)
Recoveries	36		16
Net (charge-offs) recoveries	(215)		(185)
Ending balance	$ 293		$ 281
As percent of ALLL	2.00%		2.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	293		281
Loans:
Individually evaluated	0		0
Collectively evaluated	27,232		23,809
Total	27,232		23,809
Net loans	26,939		23,528
Originated | Commercial portfolio segment | Commercial & industrial
Allowance for Loan Losses (ALLL):
Beginning balance	4,683	4,192	4,192
Provision	395		1,262
Charge-offs	(59)		(813)
Recoveries	90		42
Net (charge-offs) recoveries	31		(771)
Ending balance	$ 5,109		$ 4,683
As percent of ALLL	42.00%		41.00%
ALLL:
Individually evaluated	$ 308		$ 0
Collectively evaluated	4,801		4,683
Loans:
Individually evaluated	722		227
Collectively evaluated	659,318		567,873
Total	660,040		568,100
Net loans	654,931		563,417
Originated | Commercial portfolio segment | Owner-occupied CRE
Allowance for Loan Losses (ALLL):
Beginning balance	2,439	2,115	2,115
Provision	(17)		385
Charge-offs	(13)		(64)
Recoveries	2		3
Net (charge-offs) recoveries	(11)		(61)
Ending balance	$ 2,411		$ 2,439
As percent of ALLL	20.00%		21.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	2,411		2,439
Loans:
Individually evaluated	1,792		321
Collectively evaluated	319,531		283,210
Total	321,323		283,531
Net loans	318,912		281,092
Originated | Commercial portfolio segment | AG production
Allowance for Loan Losses (ALLL):
Beginning balance	110	112	112
Provision	84		(2)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 194		$ 110
As percent of ALLL	1.00%		1.00%
ALLL:
Individually evaluated	$ 119		$ 0
Collectively evaluated	75		110
Loans:
Individually evaluated	1,095		0
Collectively evaluated	10,355		11,113
Total	11,450		11,113
Net loans	11,256		11,003
Originated | Commercial real estate portfolio segment | AG real estate
Allowance for Loan Losses (ALLL):
Beginning balance	255	235	235
Provision	45		20
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 300		$ 255
As percent of ALLL	2.00%		2.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	300		255
Loans:
Individually evaluated	878		0
Collectively evaluated	37,738		31,374
Total	38,616		31,374
Net loans	38,316		31,119
Originated | Commercial real estate portfolio segment | CRE investment
Allowance for Loan Losses (ALLL):
Beginning balance	1,230	1,154	1,154
Provision	68		113
Charge-offs	0		(37)
Recoveries	0		0
Net (charge-offs) recoveries	0		(37)
Ending balance	$ 1,298		$ 1,230
As percent of ALLL	11.00%		11.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	1,298		1,230
Loans:
Individually evaluated	0		0
Collectively evaluated	180,427		171,087
Total	180,427		171,087
Net loans	179,129		169,857
Originated | Commercial real estate portfolio segment | Construction & land development
Allowance for Loan Losses (ALLL):
Beginning balance	431	628	628
Provision	(111)		(197)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 320		$ 431
As percent of ALLL	3.00%		4.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	320		431
Loans:
Individually evaluated	0		0
Collectively evaluated	52,806		66,478
Total	52,806		66,478
Net loans	52,486		66,047
Originated | Residential | Residential first mortgage
Allowance for Loan Losses (ALLL):
Beginning balance	1,400	1,297	1,297
Provision	(42)		187
Charge-offs	0		(85)
Recoveries	36		1
Net (charge-offs) recoveries	36		(84)
Ending balance	$ 1,394		$ 1,400
As percent of ALLL	12.00%		12.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	1,394		1,400
Loans:
Individually evaluated	0		0
Collectively evaluated	228,312		220,368
Total	228,312		220,368
Net loans	226,918		218,968
Originated | Residential | Residential junior mortgage
Allowance for Loan Losses (ALLL):
Beginning balance	408	409	409
Provision	22		(31)
Charge-offs	(20)		0
Recoveries	27		30
Net (charge-offs) recoveries	7		30
Ending balance	$ 437		$ 408
As percent of ALLL	4.00%		4.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	437		408
Loans:
Individually evaluated	0		0
Collectively evaluated	89,241		78,379
Total	89,241		78,379
Net loans	88,804		77,971
Originated | Residential | Residential construction
Allowance for Loan Losses (ALLL):
Beginning balance	211	200	200
Provision	323		11
Charge-offs	(226)		0
Recoveries	0		0
Net (charge-offs) recoveries	(226)		0
Ending balance	$ 308		$ 211
As percent of ALLL	3.00%		2.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	308		211
Loans:
Individually evaluated	0		0
Collectively evaluated	41,246		30,926
Total	41,246		30,926
Net loans	40,938		30,715
Acquired
Allowance for Loan Losses (ALLL):
Beginning balance	1,705	2,111	2,111
Provision	(94)		(414)
Charge-offs	(60)		(13)
Recoveries	5		21
Net (charge-offs) recoveries	(55)		8
Ending balance	$ 1,556		$ 1,705
As percent of ALLL	100.00%		100.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	1,556		1,705
Loans:
Individually evaluated	8,251		9,391
Collectively evaluated	583,987		671,625
Total	592,238		681,016
Net loans	590,682		679,311
Acquired | Retail & other
Allowance for Loan Losses (ALLL):
Beginning balance	23	25	25
Provision	(2)		1
Charge-offs	0		(3)
Recoveries	0		0
Net (charge-offs) recoveries	0		(3)
Ending balance	$ 21		$ 23
As percent of ALLL	1.00%		1.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	21		23
Loans:
Individually evaluated	12		12
Collectively evaluated	1,469		2,672
Total	1,481		2,684
Net loans	1,460		2,661
Acquired | Commercial portfolio segment | Commercial & industrial
Allowance for Loan Losses (ALLL):
Beginning balance	588	742	742
Provision	(39)		(155)
Charge-offs	0		0
Recoveries	0		1
Net (charge-offs) recoveries	0		1
Ending balance	$ 549		$ 588
As percent of ALLL	35.00%		34.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	549		588
Loans:
Individually evaluated	1,421		2,700
Collectively evaluated	102,281		114,120
Total	103,702		116,820
Net loans	103,153		116,232
Acquired | Commercial portfolio segment | Owner-occupied CRE
Allowance for Loan Losses (ALLL):
Beginning balance	408	492	492
Provision	(40)		(85)
Charge-offs	0		(10)
Recoveries	0		11
Net (charge-offs) recoveries	0		1
Ending balance	$ 368		$ 408
As percent of ALLL	24.00%		24.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	368		408
Loans:
Individually evaluated	760		1,185
Collectively evaluated	134,425		156,637
Total	135,185		157,822
Net loans	134,817		157,414
Acquired | Commercial portfolio segment | AG production
Allowance for Loan Losses (ALLL):
Beginning balance	11	17	17
Provision	1		(6)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 12		$ 11
As percent of ALLL	1.00%		1.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	12		11
Loans:
Individually evaluated	156		0
Collectively evaluated	24,444		24,512
Total	24,600		24,512
Net loans	24,588		24,501
Acquired | Commercial real estate portfolio segment | AG real estate
Allowance for Loan Losses (ALLL):
Beginning balance	46	61	61
Provision	1		(15)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 47		$ 46
As percent of ALLL	3.00%		3.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	47		46
Loans:
Individually evaluated	211		222
Collectively evaluated	19,764		21,848
Total	19,975		22,070
Net loans	19,928		22,024
Acquired | Commercial real estate portfolio segment | CRE investment
Allowance for Loan Losses (ALLL):
Beginning balance	240	234	234
Provision	(36)		6
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 204		$ 240
As percent of ALLL	13.00%		14.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	204		240
Loans:
Individually evaluated	2,483		1,686
Collectively evaluated	153,532		170,879
Total	156,015		172,565
Net loans	155,811		172,325
Acquired | Commercial real estate portfolio segment | Construction & land development
Allowance for Loan Losses (ALLL):
Beginning balance	79	98	98
Provision	(29)		(19)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 50		$ 79
As percent of ALLL	3.00%		5.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	50		79
Loans:
Individually evaluated	427		603
Collectively evaluated	8,577		13,518
Total	9,004		14,121
Net loans	8,954		14,042
Acquired | Residential | Residential first mortgage
Allowance for Loan Losses (ALLL):
Beginning balance	246	312	312
Provision	(33)		(70)
Charge-offs	0		0
Recoveries	0		4
Net (charge-offs) recoveries	0		4
Ending balance	$ 213		$ 246
As percent of ALLL	14.00%		14.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	213		246
Loans:
Individually evaluated	2,560		2,750
Collectively evaluated	112,528		134,723
Total	115,088		137,473
Net loans	114,875		137,227
Acquired | Residential | Residential junior mortgage
Allowance for Loan Losses (ALLL):
Beginning balance	64	79	79
Provision	49		(20)
Charge-offs	(60)		0
Recoveries	5		5
Net (charge-offs) recoveries	(55)		5
Ending balance	$ 58		$ 64
As percent of ALLL	4.00%		4.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	58		64
Loans:
Individually evaluated	221		233
Collectively evaluated	26,717		32,716
Total	26,938		32,949
Net loans	26,880		32,885
Acquired | Residential | Residential construction
Allowance for Loan Losses (ALLL):
Beginning balance	0	$ 51	51
Provision	34		(51)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 34		$ 0
As percent of ALLL	2.00%		0.00%
ALLL:
Individually evaluated	$ 0		$ 0
Collectively evaluated	34		0
Loans:
Individually evaluated	0		0
Collectively evaluated	250		0
Total	250		0
Net loans	$ 216		$ 0