Equity Incentive Plan - Summary of Company's Restricted Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended	6 Months Ended
	May 16, 2017	May 17, 2016	Jan. 04, 2016	Jun. 30, 2017	Jun. 30, 2017
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted					60,605
Expected future compensation expense				$ 416	$ 416
Expected future compensation expense, restricted shares vesting period					3 years 29 days
Restricted Stock [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Nonvested at beginning of period				42,138	37,050
Number of Restricted Shares, Granted	6,804	12,285	2,730		17,898
Number of Restricted Shares, Vested					(12,810)
Number of Restricted Shares, Forfeited				0	0
Number of Restricted Shares, Nonvested at June 30, 2017				42,138	42,138
Weighted Average Grant Date Fair Value, Nonvested at beginning of period				$ 15.60	$ 10.77
Weighted Average Grant Date Fair Value, Granted					22.15
Weighted Average Grant Date Fair Value, Vested					10.76
Weighted Average Grant Date Fair Value, Forfeited				0	0
Weighted Average Grant Date Fair Value, Nonvested at June 30, 2017				$ 15.60	$ 15.60
Restricted Shares Awarded in 2015 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted					16,699
Expected future compensation expense				$ 18	$ 18
Expected future compensation expense, restricted shares vesting period					6 months
Restricted Shares Awarded in 2016 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted					15,748
Expected future compensation expense				50	$ 50
Expected future compensation expense, restricted shares vesting period					1 year 6 months
Restricted Shares Awarded in 2017 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted					11,713
Expected future compensation expense				146	$ 146
Expected future compensation expense, restricted shares vesting period					2 years 6 months
Restricted Shares Awarded in 2018 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted					10,260
Expected future compensation expense				77	$ 77
Expected future compensation expense, restricted shares vesting period					3 years 6 months
Restricted Shares Awarded in 2019 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted					6,185
Expected future compensation expense				$ 125	$ 125
Expected future compensation expense, restricted shares vesting period					4 years 6 months