Fair Value - Assets Measured on Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Specific allowance for loan losses	$ (14,882)	$ (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	8,337	9,454
Foreclosed assets remeasured at initial recognition:
Fair value of foreclosed assets	852	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	334	88
Specific allowance for loan losses	(177)	(15)
Fair value of impaired loans	157	73
Foreclosed assets remeasured at initial recognition:
Carrying value of foreclosed assets prior to remeasurement	0	969
Charge-offs	0	(29)
Fair value of foreclosed assets	$ 0	$ 940