Share-Based Compensation - Summary of Company's Restricted Stock Activity (Detail)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Restricted Stock
Number of Shares
Balance at beginning of period (in shares) | shares	22,982
Granted (in shares) | shares	10,945
Vested (in shares) | shares	(22,856)
Forfeited (in shares) | shares	0
Balance at end of period (in shares) | shares	11,071
Weighted Average Price
Balance at beginning of period (in usd per share) | $ / shares	$ 14.44
Granted (in usd per share) | $ / shares	20.55
Vested (in usd per share) | $ / shares	14.46
Forfeited (in usd per share) | $ / shares	0.00
Balance of end of period (in usd per share) | $ / shares	$ 20.44
RSUs
Number of Shares
Balance at beginning of period (in shares) | shares	267,732
Granted (in shares) | shares	153,233
Vested (in shares) | shares	(118,921)
Forfeited (in shares) | shares	(6,697)
Balance at end of period (in shares) | shares	295,347
Weighted Average Price
Balance at beginning of period (in usd per share) | $ / shares	$ 13.93
Granted (in usd per share) | $ / shares	19.14
Vested (in usd per share) | $ / shares	13.77
Forfeited (in usd per share) | $ / shares	18.88
Balance of end of period (in usd per share) | $ / shares	$ 16.58