Investment Securities - Allowance for Credit Losses HTM (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	$ 0
Provision for credit loss expense	2,546	$ 0	$ 0
Ending balance	2,915	0
State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	0
Provision for credit loss expense	2,249
Ending balance	2,307	0
Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	0
Provision for credit loss expense	297
Ending balance	608	0
Impact of ASU 2016-13 adoption
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	369
Ending balance		369
Impact of ASU 2016-13 adoption | State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	58
Ending balance		58
Impact of ASU 2016-13 adoption | Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning balance	$ 311
Ending balance		$ 311