Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Number of Options Outstanding
Number of Options Outstanding, Beginning balance (in shares)	145,625
Granted (in shares)	0
Exercised (in shares)	0
Canceled (in shares)	0
Expired (in shares)	0
Number of Options Outstanding, Ending balance (in shares)	145,625
Options vested or expected to vest, Outstanding (in shares)	145,625
Exercisable, Outstanding (in shares)	145,625
Weighted Average Exercise Price
Weighted Average Exercise Price, Beginning balance (in dollars per share)	$ 18.96
Granted (in dollars per share)	0
Exercised (in dollars per share)	0
Canceled (in dollars per share)	0
Expired (in dollars per share)	0
Weighted Average Exercise Price, Ending balance (in dollars per share)	18.96
Options vested or expected to vest, Weighted Average Exercise Price (in dollars per share)	18.96
Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0
Option Outstanding, Remaining Contractual Life in Years	1 year 9 months 18 days	2 years
Options vested or expected to vest, Remaining Contractual Life in Years	1 year 9 months 18 days
Options Outstanding, Aggregate Intrinsic Value	$ 0	$ 0
Options vested or expected to vest, Aggregate Intrinsic Value	$ 0