Investment Securities - Summary of held-to-maturity securities in unrealized loss position (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	$ 48,007	$ 13,641
Unrealized Loss, Less than 12 Months	160	107
Fair Value, 12 Months or More	49,922	174,812
Unrealized Loss, 12 Months or More	684	7,274
Fair Value, Total	97,929	188,453
Unrealized Loss, Total	844	7,381
State and political subdivisions
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	10,117	7,062
Unrealized Loss, Less than 12 Months	9	46
Fair Value, 12 Months or More	0	34,146
Unrealized Loss, 12 Months or More	0	2,145
Fair Value, Total	10,117	41,208
Unrealized Loss, Total	9	2,191
Residential mortgage-backed securities, Agency
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	16,049	6,579
Unrealized Loss, Less than 12 Months	64	61
Fair Value, 12 Months or More	48,237	136,376
Unrealized Loss, 12 Months or More	630	5,033
Fair Value, Total	64,286	142,955
Unrealized Loss, Total	694	5,094
Commercial mortgage-backed, Agency
Summary of held to maturity securities in an unrealized loss position
Fair Value, Less than 12 Months	21,841	0
Unrealized Loss, Less than 12 Months	87	0
Fair Value, 12 Months or More	1,685	4,290
Unrealized Loss, 12 Months or More	54	96
Fair Value, Total	23,526	4,290
Unrealized Loss, Total	$ 141	$ 96