Estimated Fair Value of Financial Instruments and Fair Value Measurement - Additional Information (Detail) $ in Thousands	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Subordinate debt	$ 118,202	$ 105,027
Non-rated
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term municipal bond	2,900
Subordinate debt	$ 2,500
Measurement Input, Discount Rate [Member] | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.05
Measurement Input, Discount Rate [Member] | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.11
Measurement Input, Cap Rate [Member] | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.04
Measurement Input, Cap Rate [Member] | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.09