Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Number of shares outstanding, Options and Stock Appreciation Rights
Number of shares outstanding, Beginning balance	3,115,972
Number of shares, Granted	457,500	[1]
Number of shares, Options/SAR units exercised	(190,871)
Number of shares, Options/SAR units forfeited or expired	(66,221)
Number of shares outstanding, Ending balance	3,316,380	[2]
Number of shares outstanding, Vested or expected to vest at end of period	3,218,030
Number of shares exercisable, Ending balance	2,031,630	[3]
Weighted-average exercise price
Weighted-average exercise price, Beginning balance	$ 16.30
Weighted average exercise price, Granted	$ 14.94	[1]
Weighted average exercise price, Options/SAR units exercised	$ 8.85
Weighted average exercise price, Options/SAR units forfeited or expired	$ 18.48
Weighted average exercise price, Ending balance	$ 16.50	[2]
Weighted average exercise price, Vested or expected to vest at end of period	$ 16.51
Weighted average exercise price, exercisable	$ 16.51	[3]
Weighted-Average Remaining Contractual Term
Weighted average remaining contractual life, Outstanding at end of period	4 years 6 months	[2]
Weighted average remaining contractual life, Vested or expected to vest at end of period	4 years 4 months 24 days
Weighted average remaining contractual life, Exercisable at end of period	3 years 3 months 18 days	[3]
Aggregate intrinsic value
Aggregate intrinsic value, Outstanding	$ 10,881,253	[2]
Aggregate intrinsic value, Vested or expected to vest	10,656,933
Aggregate intrinsic value, Exercisable	$ 8,047,463	[3]

[1] Includes 325,500 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 2,946,669 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 1,894,343 shares of the Company's common stock issuable upon exercise.