Fair Value Disclosures - Assets Measured at Fair Value on Non-recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	$ 1,433	$ 1,843
Total assets	1,801		$ 2,014
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	27,674	28,351
Impaired leases held for investment	1,250	1,250
Other real estate owned	1,433	1,843
Total assets	30,357	31,444
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	0	0
Impaired leases held for investment	0	0
Other real estate owned	0	0
Total assets	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	0	0
Impaired leases held for investment	0	0
Other real estate owned	0	0
Total assets	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans held for investment	27,674	28,351
Impaired leases held for investment	1,250	1,250
Other real estate owned	1,433	1,843
Total assets	$ 30,357	$ 31,444