Fair Value Disclosures - Assets Measured at Fair Value on Non-recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	$ 1,187	$ 1,843
Total assets	1,779	1,958
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	25,166	28,351
Impaired leases held for investment		1,250
Other real estate owned	1,187	1,843
Total assets	26,353	31,444
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	0	0
Impaired leases held for investment		0
Other real estate owned	0	0
Total assets	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	0	0
Impaired leases held for investment		0
Other real estate owned	0	0
Total assets	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	25,166	28,351
Impaired leases held for investment		1,250
Other real estate owned	1,187	1,843
Total assets	$ 26,353	$ 31,444