Estimated Fair Value of Financial Instruments and Fair Value Measurement - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term municipal bond	$ 16,100
Subordinate debt	104,872	$ 104,784
Non-rated [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Subordinate debt	$ 1,000
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rates	5.00%
Capitalization rates	5.00%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rates	11.00%
Capitalization rates	10.00%