Loans, Allowance for Credit Losses - Loans, and Credit Quality - Summary of changes in ACL-Loans by portfolio segment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
ACL-Loans:
Beginning balance	$ 13,972	$ 13,153	$ 13,153
Provision	3,000	200	1,200
Charge-offs	(93)	(10)	(927)
Recoveries	38	27	546
Net (charge-offs) recoveries	(55)	17	(381)
Ending balance	$ 26,202	13,370	$ 13,972
As % of ACL-Loans	100.00%		100.00%
Retail & other
ACL-Loans:
Beginning balance	$ 344	304	$ 304
Provision	27		338
Charge-offs	(73)		(347)
Recoveries	4		49
Net (charge-offs) recoveries	(69)		(298)
Ending balance	$ 436		$ 344
As % of ACL-Loans	2.00%		2.00%
Commercial portfolio segment \| Commercial & industrial
ACL-Loans:
Beginning balance	$ 5,471	5,271	$ 5,271
Provision	1,253		(61)
Charge-offs	0		(159)
Recoveries	30		420
Net (charge-offs) recoveries	30		261
Ending balance	$ 10,513		$ 5,471
As % of ACL-Loans	40.00%		39.00%
Commercial portfolio segment \| Owner-occupied CRE
ACL-Loans:
Beginning balance	$ 3,010	2,847	$ 2,847
Provision	163		254
Charge-offs	0		(93)
Recoveries	0		2
Net (charge-offs) recoveries	0		(91)
Ending balance	$ 4,422		$ 3,010
As % of ACL-Loans	17.00%		22.00%
Commercial portfolio segment \| Agricultural
ACL-Loans:
Beginning balance	$ 579	422	$ 422
Provision	95		157
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 1,035		$ 579
As % of ACL-Loans	4.00%		4.00%
Commercial real estate portfolio segment \| CRE investment
ACL-Loans:
Beginning balance	$ 1,600	1,470	$ 1,470
Provision	795		130
Charge-offs	(20)		0
Recoveries	0		0
Net (charge-offs) recoveries	(20)		0
Ending balance	$ 4,345		$ 1,600
As % of ACL-Loans	16.00%		11.00%
Commercial real estate portfolio segment \| Construction & land development
ACL-Loans:
Beginning balance	$ 414	510	$ 510
Provision	82		(96)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs) recoveries	0		0
Ending balance	$ 547		$ 414
As % of ACL-Loans	2.00%		3.00%
Residential \| Residential first mortgage
ACL-Loans:
Beginning balance	$ 1,669	1,646	$ 1,646
Provision	533		9
Charge-offs	0		(22)
Recoveries	1		36
Net (charge-offs) recoveries	1		14
Ending balance	$ 3,489		$ 1,669
As % of ACL-Loans	13.00%		12.00%
Residential \| Residential junior mortgage
ACL-Loans:
Beginning balance	$ 517	472	$ 472
Provision	102		86
Charge-offs	0		(80)
Recoveries	3		39
Net (charge-offs) recoveries	3		(41)
Ending balance	$ 973		$ 517
As % of ACL-Loans	4.00%		4.00%
Residential \| Residential construction
ACL-Loans:
Beginning balance	$ 368	$ 211	$ 211
Provision	(50)		383
Charge-offs	0		(226)
Recoveries	0		0
Net (charge-offs) recoveries	0		(226)
Ending balance	$ 442		$ 368
As % of ACL-Loans	2.00%		3.00%
Adoption of CECL
ACL-Loans:
Beginning balance	$ 8,488
Ending balance			$ 8,488
Adoption of CECL \| Retail & other
ACL-Loans:
Beginning balance	134
Ending balance			134
Adoption of CECL \| Commercial portfolio segment \| Commercial & industrial
ACL-Loans:
Beginning balance	2,962
Ending balance			2,962
Adoption of CECL \| Commercial portfolio segment \| Owner-occupied CRE
ACL-Loans:
Beginning balance	1,249
Ending balance			1,249
Adoption of CECL \| Commercial portfolio segment \| Agricultural
ACL-Loans:
Beginning balance	361
Ending balance			361
Adoption of CECL \| Commercial real estate portfolio segment \| CRE investment
ACL-Loans:
Beginning balance	1,970
Ending balance			1,970
Adoption of CECL \| Commercial real estate portfolio segment \| Construction & land development
ACL-Loans:
Beginning balance	51
Ending balance			51
Adoption of CECL \| Residential \| Residential first mortgage
ACL-Loans:
Beginning balance	1,286
Ending balance			1,286
Adoption of CECL \| Residential \| Residential junior mortgage
ACL-Loans:
Beginning balance	351
Ending balance			351
Adoption of CECL \| Residential \| Residential construction
ACL-Loans:
Beginning balance	124
Ending balance			124
Initial PCD ACL
ACL-Loans:
Beginning balance	797
Ending balance			797
Initial PCD ACL \| Retail & other
ACL-Loans:
Beginning balance	0
Ending balance			0
Initial PCD ACL \| Commercial portfolio segment \| Commercial & industrial
ACL-Loans:
Beginning balance	797
Ending balance			797
Initial PCD ACL \| Commercial portfolio segment \| Owner-occupied CRE
ACL-Loans:
Beginning balance	0
Ending balance			0
Initial PCD ACL \| Commercial portfolio segment \| Agricultural
ACL-Loans:
Beginning balance	0
Ending balance			0
Initial PCD ACL \| Commercial real estate portfolio segment \| CRE investment
ACL-Loans:
Beginning balance	0
Ending balance			0
Initial PCD ACL \| Commercial real estate portfolio segment \| Construction & land development
ACL-Loans:
Beginning balance	0
Ending balance			0
Initial PCD ACL \| Residential \| Residential first mortgage
ACL-Loans:
Beginning balance	0
Ending balance			0
Initial PCD ACL \| Residential \| Residential junior mortgage
ACL-Loans:
Beginning balance	0
Ending balance			0
Initial PCD ACL \| Residential \| Residential construction
ACL-Loans:
Beginning balance	$ 0
Ending balance			$ 0

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