Investment Securities - Allowance for Credit Losses AFS (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 609	$ 0
Credit losses on securities not previously recorded	1,160	1,208
Reduction due to sales	(294)	(244)
Net decrease in allowance on previously impaired securities	(267)	(129)
Ending balance, September 30, 2020	1,208	$ 1,208	$ 0
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Impact of ASU 2016-13 adoption
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		$ 373
Ending balance, September 30, 2020			$ 373
State and political subdivisions
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	371	0
Credit losses on securities not previously recorded	1,137	1,130
Reduction due to sales	(294)	(244)
Net decrease in allowance on previously impaired securities	(66)	(111)
Ending balance, September 30, 2020	1,148	1,148	0
State and political subdivisions | Impact of ASU 2016-13 adoption
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		373
Ending balance, September 30, 2020			373
Other securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	238	0
Credit losses on securities not previously recorded	23	78
Reduction due to sales	0	0
Net decrease in allowance on previously impaired securities	(201)	(18)
Ending balance, September 30, 2020	$ 60	60	0
Other securities | Impact of ASU 2016-13 adoption
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		$ 0
Ending balance, September 30, 2020			$ 0