Investment Securities - Allowance for Credit Losses HTM (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	$ 0
Provision for credit loss expense	40
Balance, March 31, 2020	409
State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	0
Provision for credit loss expense	39
Balance, March 31, 2020	97
Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	0
Provision for credit loss expense	1
Balance, March 31, 2020	312
Impact of adoption of 2016-13
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	369
Impact of adoption of 2016-13 | State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	58
Impact of adoption of 2016-13 | Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	$ 311