Summary of Stock Options Outstanding (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning of period, Number of Options Granted	787,450
Options granted, Number of Options Granted
Options forfeited, Number of Options Granted	(3,000)
Options exercised, Number of Options Granted	(133,200)
Options expired, Number of Options Granted	(9,000)
Outstanding, end of period, Number of Options Granted	642,250
Exercisable, end of period, Number of Options Granted	642,250
Vested or expected to vest, end of period, Number of Options Granted	642,250
Outstanding, beginning of period, Weighted Average Exercise Price	$ 14.55
Options granted, Weighted Average Exercise Price
Options forfeited, Weighted Average Exercise Price	$ 26.84
Options exercised, Weighted Average Exercise Price	$ 5.99
Options expired, Weighted Average Exercise Price	$ 26.84
Outstanding, end of period, Weighted Average Exercise Price	$ 16.09
Exercisable, end of period, Weighted Average Exercise Price	$ 16.09
Vested or expected to vest, end of period, Weighted Average Exercise Price	$ 16.09
Outstanding, end of period, Weighted Average Remaining Contractual Term (Years)	2 years 7 months 17 days
Exercisable, end of period, Weighted Average Remaining Contractual Term (Years)	2 years 7 months 17 days
Vested or expected to vest, end of period, Weighted Average Remaining Contractual Term (Years)	2 years 7 months 17 days
Outstanding, end of period, Aggregate Intrinsic Value	$ 1,635
Exercisable, end of period, Aggregate Intrinsic Value	1,635
Vested or expected to vest, end of period, Aggregate Intrinsic Value	$ 1,635