Summary of Information about Stock Appreciation Units Outstanding (Detail) (Stock Appreciation Rights (SARs), USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Stock Appreciation Rights (SARs)
Number of Units
Vested and expected to vest	207,396
Exercisable	181,913
Weighted-Average Exercise Price
Vested and expected to vest	$ 7.03
Exercisable	$ 6.71
Weighted Average Remaining Contractual Term
Vested and expected to vest	5 years 10 months 10 days
Exercisable	5 years 8 months 9 days
Aggregate Intrinsic Value
Vested and expected to vest	$ 101
Exercisable	$ 98