Stock-Based Compensation - Summary of Stock Appreciation Rights (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Time-Based Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate Intrinsic Value, Outstanding ending balance	$ 9,674
Aggregate Intrinsic Value, Exercisable	8,316
Aggregate Intrinsic Value, Vested and expected to vest	9,674
Number of Shares, Beginning balance	3,611,567
Number of Shares, Granted	54,000
Number of Shares, Exercised	(10,700)
Number of Shares, Forfeited or expired	(39,800)
Number of Shares, Ending balance	3,615,067
Number of Shares, Exercisable	2,767,700
Number of Shares, Vested and expected to vest	3,615,067
Weighted-Average Exercise Price, Outstanding beginning balance	$ 4.20
Weighted-Average Exercise Price, Granted	$ 7.62
Weighted-Average Exercise Price, Exercised	$ 2.31
Weighted-Average Exercise Price, Forfeited or expired	$ 5.05
Weighted-Average Exercise Price, Outstanding ending balance	$ 4.25
Weighted-Average Exercise Price, Exercisable	$ 3.95
Weighted-Average Exercise Price, Vested and expected to vest	$ 4.25
Weighted-Average Remaining Contractual Term, Outstanding	6 years 8 months 16 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 11 months 5 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 8 months 16 days
Performance-Based Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate Intrinsic Value, Outstanding ending balance	2,101
Aggregate Intrinsic Value, Exercisable	2,101
Aggregate Intrinsic Value, Vested and expected to vest	$ 2,101
Number of Shares, Beginning balance	865,713
Number of Shares, Granted	0
Number of Shares, Exercised	(39,362)
Number of Shares, Forfeited or expired	(13,600)
Number of Shares, Ending balance	812,751
Number of Shares, Exercisable	812,751
Number of Shares, Vested and expected to vest	812,751
Weighted-Average Exercise Price, Outstanding beginning balance	$ 5.37
Weighted-Average Exercise Price, Exercised	$ 3.55
Weighted-Average Exercise Price, Forfeited or expired	$ 6.33
Weighted-Average Exercise Price, Outstanding ending balance	$ 5.44
Weighted-Average Exercise Price, Exercisable	$ 5.44
Weighted-Average Exercise Price, Vested and expected to vest	$ 5.44
Weighted-Average Remaining Contractual Term, Outstanding	6 years 1 month 28 days
Weighted-Average Remaining Contractual Term, Exercisable	6 years 1 month 28 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 1 month 28 days