Stock-based Compensation - Summary of Stock Appreciation Rights (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Time-Based Stock Appreciation Rights [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning Balance	4,109,184
Number of Shares, Granted	0
Number of Shares, Exercised	(44,600)
Number of Shares, Outstanding, Ending Balance	4,064,584
Number of Shares, Exercisable	3,855,317
Number of Shares, Vested and expected to vest	4,064,584
Weighted-Average Exercise Price, Outstanding, Beginning Balance | $ / shares	$ 5.22
Weighted-Average Exercise Price, Exercised | $ / shares	4.72
Weighted-Average Exercise Price, Outstanding, Ending Balance | $ / shares	5.28
Weighted-Average Exercise Price, Exercisable | $ / shares	5.26
Weighted-Average Exercise Price, Vested and expected to vest | $ / shares	$ 5.28
Weighted-Average Remaining Contractual Term, Outstanding	5 years 4 months 21 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 1 month 24 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	5 years 4 months 21 days
Aggregate Intrinsic Value, Outstanding, Ending balance | $	$ 22,031
Aggregate Intrinsic Value, Exercisable | $	21,376
Aggregate Intrinsic Value, Vested and expected to vest | $	$ 22,031
Performance-Based Stock Appreciation Rights [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning Balance	778,774
Number of Shares, Granted	0
Number of Shares, Exercised	(400)
Number of Shares, Forfeited or expired	(1,000)
Number of Shares, Outstanding, Ending Balance	777,374
Number of Shares, Exercisable	777,374
Number of Shares, Vested and expected to vest	777,374
Weighted-Average Exercise Price, Outstanding, Beginning Balance | $ / shares	$ 6.33
Weighted-Average Exercise Price, Exercised | $ / shares	2.87
Weighted-Average Exercise Price, Forfeited or expired | $ / shares	5.65
Weighted-Average Exercise Price, Outstanding, Ending Balance | $ / shares	6.33
Weighted-Average Exercise Price, Exercisable | $ / shares	6.33
Weighted-Average Exercise Price, Vested and expected to vest | $ / shares	$ 6.33
Weighted-Average Remaining Contractual Term, Outstanding	4 years 1 month 13 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 1 month 13 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	4 years 1 month 13 days
Aggregate Intrinsic Value, Outstanding, Ending balance | $	$ 3,752
Aggregate Intrinsic Value, Exercisable | $	3,752
Aggregate Intrinsic Value, Vested and expected to vest | $	$ 3,752