Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Number of shares outstanding, Option
Number of shares outstanding, Beginning balance	2,546,117
Number of shares, Granted	825,750	[1]
Number of shares outstanding, Ending balance	3,115,972	[2]
Number of shares outstanding, Vested or expected to vest at end of period	3,008,858
Number of shares exercisable, Ending balance	1,595,611	[3]
Weighted-average exercise price
Weighted-average exercise price, Beginning balance	$ 15.88
Weighted average exercise price, Granted	$ 16.67	[1]
Weighted average exercise price, Ending balance	$ 16.30	[2]
Weighted average exercise price, Vested or expected to vest at end of period	$ 16.25
Weighted average exercise price, exercisable	$ 14.79	[3]
Weighted-Average Remaining Contractual Term
Weighted average remaining contractual life, Outstanding at end of period	4 years 9 months 18 days	[2]
Weighted average remaining contractual life, Vested or expected to vest at end of period	4 years 8 months 12 days
Weighted average remaining contractual life, Exercisable at end of period	3 years 2 months 12 days	[3]
Aggregate intrinsic value
Aggregate intrinsic value, Outstanding	$ 5,785,501	[2]
Aggregate intrinsic value, Vested or expected to vest	5,778,854
Aggregate intrinsic value, Exercisable	$ 5,675,797	[3]
Stock Appreciation Rights (SARs)
Number of shares outstanding, Option
Number of shares, Granted	693,750
Number of shares, Options/SAR units exercised	(151,867)
Number of shares, Options/SAR units forfeited or expired	(104,028)
Weighted-average exercise price
Weighted average exercise price, Options/SAR units exercised	$ 8.10
Weighted average exercise price, Options/SAR units forfeited or expired	$ 20.94

[1] Includes 693,750 SAR units which are convertible for a maximum number of shares of the Company's common stock equal to 75% of the SAR units subject to the grant.

[2] Due to the ceiling imposed on the SAR grants, the outstanding amount equals a maximum of 2,816,691 shares of the Company's common stock issuable upon exercise.

[3] Due to the ceiling imposed on the SAR grants, the exercisable amount equals a maximum of 1,549,633 shares of the Company's common stock issuable upon exercise.