Equity Incentive Plan - Summary of Company's Restricted Stock (Detail) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		40,692
Expected future remaining compensation expense | $	$ 558	$ 558
Expected future compensation expense, restricted shares remaining vesting period		2 years 6 months 29 days
Restricted Shares Awarded on January 15, 2016 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		6,160
Date of Award		Jan. 15, 2016
Expected future remaining compensation expense | $	54	$ 54
Expected future compensation expense, restricted shares remaining vesting period		2 years 6 months
Restricted Shares Awarded on March 11, 2016 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		5,256
Date of Award		Mar. 11, 2016
Expected future remaining compensation expense | $	16	$ 16
Expected future compensation expense, restricted shares remaining vesting period		6 months
Restricted Shares Awarded on March 20, 2017 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		7,814
Date of Award		Mar. 20, 2017
Expected future remaining compensation expense | $	81	$ 81
Expected future compensation expense, restricted shares remaining vesting period		1 year 6 months
Restricted Shares Awarded on March 20, 2017 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		4,952
Date of Award		Mar. 20, 2017
Expected future remaining compensation expense | $	93	$ 93
Expected future compensation expense, restricted shares remaining vesting period		3 years 6 months
Restricted Shares Awarded on April 10, 2018 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		8,294
Date of Award		Apr. 10, 2018
Expected future remaining compensation expense | $	145	$ 145
Expected future compensation expense, restricted shares remaining vesting period		2 years 6 months
Restricted Shares Awarded on April 10, 2018 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		8,216
Date of Award		Apr. 10, 2018
Expected future remaining compensation expense | $	$ 169	$ 169
Expected future compensation expense, restricted shares remaining vesting period		4 years 6 months
Restricted Stock [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Nonvested at beginning of period	24,182	42,138
Number of Restricted Shares, Granted	16,510	16,510
Number of Restricted Shares, Vested	0	(17,956)
Number of Restricted Shares, Forfeited	0	0
Number of Restricted Shares, Nonvested at end of period	40,692	40,692
Weighted Average Grant Date Fair Value, Nonvested at beginning of period | $ / shares	$ 16.78	$ 15.60
Weighted Average Grant Date Fair Value, Granted | $ / shares	22.51	22.51
Weighted Average Grant Date Fair Value, Vested | $ / shares	0	14.01
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	0	0
Weighted Average Grant Date Fair Value, Nonvested at end of period | $ / shares	$ 19.11	$ 19.11