Stock-Based Compensation - Summary of Stock Appreciation Rights (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Time-Based Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning balance	3,422,967
Number of Shares, Granted	755,500
Number of Shares, Exercised	(418,900)
Number of Shares, Forfeited or expired	(148,000)
Number of Shares, Ending balance	3,611,567
Number of Shares, Exercisable	2,744,400
Number of Shares, Vested and expected to vest	3,611,567
Weighted-Average Exercise Price, Outstanding beginning balance	$ 3.72
Weighted-Average Exercise Price, Granted	$ 5.35
Weighted-Average Exercise Price, Exercised	$ 2.59
Weighted-Average Exercise Price, Forfeited or expired	$ 3.43
Weighted-Average Exercise Price, Outstanding ending balance	$ 4.20
Weighted-Average Exercise Price, Exercisable	$ 3.92
Weighted-Average Exercise Price, Vested and expected to vest	$ 4.20
Weighted-Average Remaining Contractual Term, Outstanding	6 years 11 months 5 days
Weighted-Average Remaining Contractual Term, Exercisable	6 years 1 month 10 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 11 months 5 days
Aggregate Intrinsic Value, Outstanding ending balance	$ 7,987
Aggregate Intrinsic Value, Exercisable	6,941
Aggregate Intrinsic Value, Vested and expected to vest	7,987
Performance-Based Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning balance	1,034,025
Number of Shares, Granted	120,500
Number of Shares, Exercised	(151,375)
Number of Shares, Forfeited or expired	(137,437)
Number of Shares, Ending balance	865,713
Number of Shares, Exercisable	836,413
Number of Shares, Vested and expected to vest	836,413
Weighted-Average Exercise Price, Outstanding beginning balance	$ 4.88
Weighted-Average Exercise Price, Granted	$ 4.20
Weighted-Average Exercise Price, Exercised	$ 2.90
Weighted-Average Exercise Price, Forfeited or expired	$ 3.39
Weighted-Average Exercise Price, Outstanding ending balance	$ 5.37
Weighted-Average Exercise Price, Exercisable	$ 5.41
Weighted-Average Exercise Price, Vested and expected to vest	$ 5.41
Weighted-Average Remaining Contractual Term, Outstanding	6 years 5 months 19 days
Weighted-Average Remaining Contractual Term, Exercisable	6 years 4 months 13 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 4 months 13 days
Aggregate Intrinsic Value, Outstanding ending balance	1,918
Aggregate Intrinsic Value, Exercisable	1,856
Aggregate Intrinsic Value, Vested and expected to vest	$ 1,856