Investment Securities - Amortized cost and estimated fair value (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Amortized Cost
Due within one year or less	$ 16,054
Due after one year through five years	25,745
Due after five years through ten years	78,317
Due after 10 years	224,488
Total investment securities available-for-sale	344,604
Fair Value
Due within one year or less	16,149
Due after one year through five years	25,934
Due after five years through ten years	80,298
Due after 10 years	231,768
Total investment securities available-for-sale	$ 354,149