Allowance for Credit Losses on Loans - Credit Quality Classification (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) item	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2020 USD ($)
Loans
Total	$ 2,554,169,000		$ 2,534,163,000
Classified
Loans
Total	$ 39,603,000	$ 25,200,000	$ 32,579,000
Percentage of financing receivable balance over total assets	0.97%	0.81%	0.79%
Commercial
Loans
Total	$ 682,280,000		$ 631,547,000
Real estate
Loans
Total			1,882,734,000
Consumer
Loans
Total			19,882,000
Commercial
Loans
Total	$ 682,280,000			$ 6,790,000
Number of lending relationships moved to classified assets | item	1
Commercial | Commercial
Loans
Total	$ 682,280,000		603,345,000
CRE
Loans
Number of lending relationships moved to classified assets | item	2
CRE - owner occupied
Loans
Total	$ 543,164,000			6,994,000
CRE - owner occupied | Real estate
Loans
Total	543,164,000		548,907,000
CRE - non-owner occupied
Loans
Total	755,008,000		767,821,000	11,672,000
CRE - non-owner occupied | Real estate
Loans
Total	755,008,000		767,821,000
Land and construction
Loans
Total	153,358,000			1,458,000
Land and construction | Real estate
Loans
Total	153,358,000		147,189,000
Home equity
Loans
Total	117,768,000			1,321,000
Home equity | Real estate
Loans
Total	117,768,000		151,775,000
Multi-family
Loans
Total	172,875,000			1,253,000
Multi-family | Real estate
Loans
Total	172,875,000		180,623,000
Residential mortgages
Loans
Total	96,271,000			678,000
Residential mortgages | Real estate
Loans
Total	96,271,000		100,759,000
Consumer and other
Loans
Total				$ 1,689,000
Consumer and other | Consumer
Loans
Total	33,445,000		33,744,000
Consumer
Loans
Total	$ 33,445,000
Consumer | Consumer
Loans
Total			$ 33,744,000