Stock-Based Compensation - Summary of Restricted Stock Awards Activity (Detail) - Restricted Stock $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Shares
Non-vested restricted stock, beginning balance (in shares) | shares	1,765,262
Granted (in shares) | shares	647,850
Vested (in shares) | shares	(672,345)
Forfeited (in shares) | shares	(232,228)
Non-vested restricted stock, ending balance (in shares) | shares	1,508,539
Weighted- Average Grant Date Fair Value Per Share
Weighted average grant date fair value per share, non-vested restricted stock, beginning balance (in dollars per share) | $ / shares	$ 5.72
Weighted average grant date fair value per share, granted (in dollars per share) | $ / shares	15.46
Weighted average grant date fair value per share, vested (in dollars per share) | $ / shares	6.37
Weighted average grant date fair value per share, forfeited (in dollars per share) | $ / shares	11.87
Weighted average grant date fair value per share, non-vested restricted stock, ending balance (in dollars per share) | $ / shares	$ 9.51
Unrecognized compensation expense | $	$ 9.5
Weighted-average remaining period for recognition of unrecognized compensation costs	2 years 2 months 12 days