Commitments and Contingencies - Summary of Distribution of Undisbursed Loan Commitments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Undisbursed loan commitments	$ 81,050	$ 63,788
Commitments to Extend Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Undisbursed loan commitments	76,094	60,789
Standby Letter of Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Undisbursed loan commitments	3,983	1,790
Commercial Letter of Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Undisbursed loan commitments	$ 973	$ 1,209