Investment Securities - Allowance for Credit Losses HTM (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	$ 2,915	$ 0
Provision for credit loss expense	(697)	40
Securities charged-off	(600)
Ending balance	1,618	409
State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	2,307	0
Provision for credit loss expense	(1,265)	39
Securities charged-off	0
Ending balance	1,042	97
Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	608	0
Provision for credit loss expense	568	1
Securities charged-off	(600)
Ending balance	$ 576	312
Cumulative Effect, Period of Adoption, Adjustment
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance		369
Cumulative Effect, Period of Adoption, Adjustment | State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance		58
Cumulative Effect, Period of Adoption, Adjustment | Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance		$ 311