Shared-Based Compensation - Reconciliation of Option Activity (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Number of Options (in thousands)
Beginning balance (in shares) | shares	771,000
Granted (in shares) | shares	210,400
Exercised (in shares) | shares	0
Forfeitures (in shares) | shares	(3,000)
Ending balance (in shares) | shares	978,000
Options exercisable (in shares) | shares	701,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (in USD per share) | $ / shares	$ 15.17
Granted (in USD per share) | $ / shares	7.93
Exercised (in USD per share) | $ / shares
Forfeitures (in USD per share) | $ / shares	24.41
Ending balance (in USD per share) | $ / shares	13.58
Options exercisable (in USD per share) | $ / shares	$ 14.27
Weighted-average remaining contractual term, outstanding	6 years 3 months 14 days
Weighted- average remaining contractual term, options exercisable	5 years
Aggregate intrinsic value, exercised | $	$ 0
Aggregate intrinsic value, outstanding | $	0
Aggregate intrinsic value, options exercisable | $	$ 0