Capital Stock - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Preferred Stock [Member]
Equity [Line Items]
Stockholders to purchase, conditions	One one-hundredth of a share of newly issued Series A Junior Participating Preferred Stock
Preferred stock purchase right	One-quarter of a preferred stock purchase right
Preferred stock exercise price	100
Minimum percentage of beneficial ownership to acquire exercisable rights	20.00%
Redemption price of rights	$ 0.001
Redemption time of rights	10 days
Expiry date of rights	Dec. 11, 2017
Employee Stock Option [Member]
Equity [Line Items]
Exercisable at end of period, Weighted Average Remaining Contractual Term	6 years
Weighted average exercise price	$ 22.35
Aggregate intrinsic value	$ 6,838	$ 1,956
Options to purchase shares of common stock	1,133,000
Employees of former affliate [Member] | Employee Stock Option [Member]
Equity [Line Items]
Exercisable at end of period, Weighted Average Remaining Contractual Term	2 years
Weighted average exercise price	$ 24.86
Aggregate intrinsic value	$ 910
Options to purchase shares of common stock	799,000