Fair Value - Assets Measured on Nonrecurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Specific allowance for loan losses	$ (16,192)	$ (13,937)		$ (12,524)
Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of impaired loans	12,256	9,454
Foreclosed assets remeasured at initial recognition:
Fair value of foreclosed assets	828	$ 1,128
Remeasured Loans | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allowance for loan losses	5,021		$ 1,337
Specific allowance for loan losses	(780)		(140)
Fair value of impaired loans	4,241		1,197
Foreclosed assets remeasured at initial recognition:
Carrying value of foreclosed assets prior to remeasurement	0		1,119
Charge-offs	0		0
Fair value of foreclosed assets	$ 0		$ 1,119