Loans and Allowance for Credit Losses on Loans - Aging of Past Due Loans by Class of Loans (Details) - USD ($)	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Aging of Past Due Loans by Class of Loans
Total Past Due	$ 11,585,000		$ 15,315,000
Current	2,693,894,000		2,518,848,000
Total loan balance	2,705,479,000		2,534,163,000
30-59 Days Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	8,216,000		4,770,000
60-89 Days Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	925,000		2,234,000
90 Days or Greater Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	2,444,000		8,311,000
Commercial
Aging of Past Due Loans by Class of Loans
Total loan balance			603,345,000
Real estate
Aging of Past Due Loans by Class of Loans
Total loan balance			1,897,074,000
Consumer
Aging of Past Due Loans by Class of Loans
Total loan balance			33,744,000
Commercial
Aging of Past Due Loans by Class of Loans
Total loan balance	897,909,000	$ 6,790,000
Commercial | Commercial
Aging of Past Due Loans by Class of Loans
Total Past Due	6,295,000		10,084,000
Current	891,614,000		593,261,000
Total loan balance	897,909,000		603,345,000
Commercial | Commercial | 30-59 Days Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	4,419,000		4,770,000
Commercial | Commercial | 60-89 Days Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	925,000		2,097,000
Commercial | Commercial | 90 Days or Greater Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	951,000		3,217,000
CRE - owner occupied
Aging of Past Due Loans by Class of Loans
Total loan balance	561,528,000	6,994,000
CRE - owner occupied | Real estate
Aging of Past Due Loans by Class of Loans
Total Past Due	3,330,000		5,094,000
Current	558,198,000		543,813,000
Total loan balance	561,528,000		548,907,000
CRE - owner occupied | Real estate | 30-59 Days Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	3,301,000
CRE - owner occupied | Real estate | 90 Days or Greater Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	29,000		5,094,000
CRE - non-owner occupied
Aging of Past Due Loans by Class of Loans
Current	713,563,000		767,821,000
Total loan balance	713,563,000	11,672,000	767,821,000
CRE - non-owner occupied | Real estate
Aging of Past Due Loans by Class of Loans
Total loan balance	713,563,000		767,821,000
Land and construction
Aging of Past Due Loans by Class of Loans
Total loan balance	142,632,000	1,458,000
Land and construction | Real estate
Aging of Past Due Loans by Class of Loans
Current	142,632,000		147,189,000
Total loan balance	142,632,000		147,189,000
Home equity
Aging of Past Due Loans by Class of Loans
Total loan balance	111,468,000	1,321,000
Home equity | Real estate
Aging of Past Due Loans by Class of Loans
Total Past Due			137,000
Current	111,468,000		151,638,000
Total loan balance	111,468,000		151,775,000
Home equity | Real estate | 60-89 Days Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due			137,000
Multi-family
Aging of Past Due Loans by Class of Loans
Total loan balance	169,791,000	1,253,000
Multi-family | Real estate
Aging of Past Due Loans by Class of Loans
Current	169,791,000		180,623,000
Total loan balance	169,791,000		180,623,000
Residential mortgages
Aging of Past Due Loans by Class of Loans
Total loan balance	91,077,000	678,000
Residential mortgages | Real estate
Aging of Past Due Loans by Class of Loans
Current	91,077,000		100,759,000
Total loan balance	91,077,000		100,759,000
Consumer and other
Aging of Past Due Loans by Class of Loans
Total loan balance	17,511,000	$ 1,689,000
Consumer and other | Consumer
Aging of Past Due Loans by Class of Loans
Total Past Due	1,960,000
Current	15,551,000		33,744,000
Total loan balance	17,511,000		$ 33,744,000
Consumer and other | Consumer | 30-59 Days Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	496,000
Consumer and other | Consumer | 90 Days or Greater Past Due
Aging of Past Due Loans by Class of Loans
Total Past Due	$ 1,464,000