Borrowed Funds - Subordinated Debt (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2007
Subordinated Debt
Balance at end of period	$ 4,124,000		$ 4,124,000		$ 4,124,000
Interest expense on borrowed funds	20,000	$ 156,000	78,000	$ 728,000
Subordinated debt redeemed			0	12,400,000	12,400,000
Subordinated Debt
Subordinated Debt
Balance at end of period	4,124,000		$ 4,124,000		4,124,000
Average balance during the period	4,124,000				12,125,000
Maximum month-end balance	$ 4,124,000				$ 17,524,000
Weighted-average rate during the period	1.94%				6.35%
Weighted-average rate at end of period	1.87%		1.87%		3.51%
Interest expense on borrowed funds			$ 78,000	$ 728,000
Subordinated debt converted, amount					$ 1,000,000.0	$ 16,000,000.0
Converted subordinated debt, shares issued					62,500	1,000,000
Annual interest expense savings					$ 970,000	$ 1,100,000
Subordinated Debt | Subordinated Debentures
Subordinated Debt
Face amount of debt issued							$ 4,000,000
Subordinated Debt | Subordinated Debentures | LIBOR
Subordinated Debt
Variable rate basis spread			1.62%