Securities - Summary of debt securities held-to-maturity in unrealized loss position (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	$ 8,558	$ 48,007
Unrealized Loss, Less than 12 Months	152	160
Fair Value, 12 Months or More	0	49,922
Unrealized Loss, 12 Months or More	0	684
Fair Value, Total	8,558	97,929
Unrealized Loss, Total	152	844
State and political subdivisions
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	4,972	10,117
Unrealized Loss, Less than 12 Months	28	9
Fair Value, 12 Months or More	0	0
Unrealized Loss, 12 Months or More	0	0
Fair Value, Total	4,972	10,117
Unrealized Loss, Total	28	9
Residential mortgage-backed securities, Agency
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	124	16,049
Unrealized Loss, Less than 12 Months	0	64
Fair Value, 12 Months or More	0	48,237
Unrealized Loss, 12 Months or More	0	630
Fair Value, Total	124	64,286
Unrealized Loss, Total	0	694
Commercial mortgage-backed, Agency
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	3,462	21,841
Unrealized Loss, Less than 12 Months	124	87
Fair Value, 12 Months or More	0	1,685
Unrealized Loss, 12 Months or More	0	54
Fair Value, Total	3,462	23,526
Unrealized Loss, Total	$ 124	$ 141