Stock-Based Compensation - Summary of Stock Appreciation Rights (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Time-Based Stock Appreciation Rights [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning Balance	2,199,094
Number of Shares, Granted	0	0
Number of Shares, Exercised	(6,000)
Number of Shares, Outstanding, Ending Balance	2,193,094
Number of Shares, Exercisable	2,163,094
Number of Shares, Vested and expected to vest	2,193,094
Weighted-Average Exercise Price, Outstanding, Beginning Balance	$ 5.36
Weighted-Average Exercise Price, Exercised	6.09
Weighted-Average Exercise Price, Outstanding, Ending Balance	5.30
Weighted-Average Exercise Price, Exercisable	5.35
Weighted-Average Exercise Price, Vested and expected to vest	$ 5.30
Weighted-Average Remaining Contractual Term, Outstanding	3 years 5 months 4 days
Weighted-Average Remaining Contractual Term, Exercisable	3 years 4 months 13 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	3 years 5 months 4 days
Aggregate Intrinsic Value, Outstanding	$ 2,483
Aggregate Intrinsic Value, Exercisable	2,709
Aggregate Intrinsic Value, Vested and expected to vest	$ 2,483
Performance-Based Stock Appreciation Rights [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning Balance	233,496
Number of Shares, Granted	0	0
Number of Shares, Outstanding, Ending Balance	233,496
Number of Shares, Exercisable	233,496
Number of Shares, Vested and expected to vest	233,496
Weighted-Average Exercise Price, Outstanding, Beginning Balance	$ 6.02
Weighted-Average Exercise Price, Outstanding, Ending Balance	5.96
Weighted-Average Exercise Price, Exercisable	5.96
Weighted-Average Exercise Price, Vested and expected to vest	$ 5.96
Weighted-Average Remaining Contractual Term, Outstanding	4 years 4 months 17 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 4 months 17 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	4 years 4 months 17 days
Aggregate Intrinsic Value, Outstanding	$ 974
Aggregate Intrinsic Value, Exercisable	974
Aggregate Intrinsic Value, Vested and expected to vest	$ 974