Summary of Significant Accounting and Reporting Policies - Reclassifications (Details) - USD ($)		12 Months Ended
	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle
Debt Securities, Held-to-maturity, Allowance for Credit Loss				$ 0
Equity balance		$ 804,580,000	$ 731,291,000	839,148,000	$ 817,605,000	$ 795,800,000	$ 810,453,000	$ 787,765,000	$ 758,033,000
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member
Allowance for credit losses, purchased with credit deterioration	$ 231,000
Accounting Standards Update 2017-08
New Accounting Pronouncements or Change in Accounting Principle
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate201708Member
Cumulative effect of accounting change
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses, purchased with credit deterioration	$ 231,000
Equity balance		$ (7,830,000)	$ (16,452,000)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle
Equity balance		80,274,000	64,797,000	$ 93,916,000	$ 77,134,000	$ 65,863,000	$ 74,477,000	$ 65,183,000	$ 57,023,000
Retained Earnings | Cumulative effect of accounting change
New Accounting Pronouncements or Change in Accounting Principle
Equity balance		$ (7,830,000)	$ (16,452,000)