Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
SARs
Granted (in shares)	300,000
Weighted- Average Remaining Contractual Term
Granted	2 years 73 days
Stock Appreciation Rights (SARs)
SARs
Outstanding at December 31, 2013 (in shares)	1,600,000
Granted (in shares)	400,000
Forfeited (in shares)	(100,000)
Exercised (in shares)	(500,000)
Outstanding at December 31, 2014 (in shares)	1,400,000	[1],[2]	1,600,000
Vested and exercisable at December 31, 2014 (in shares)	600,000	[1]
Per Share Weighted- Average Exercise Price
Outstanding at December 31, 2013 (in Dollars per share)	$ 34.14
Granted (in Dollars per share)	$ 64.64
Exercised (in Dollars per share)	$ 24.12
Outstanding at December 31, 2014 (in Dollars per share)	$ 44.44	[1],[2]	$ 34.14
Vested and exercisable at December 31, 2014 (in Dollars per share)	$ 33.36	[1]
Per Share Weighted- Average Grant Date Fair Value
Outstanding at December 31, 2013 (in Dollars per share)	$ 11.63
Granted (in Dollars per share)	$ 14.99
Exercised (in Dollars per share)	$ 8.82
Outstanding at December 31, 2014 (in Dollars per share)	$ 13.26	[1],[2]	$ 11.63
Vested and exercisable at December 31, 2014 (in Dollars per share)	$ 11.62	[1]
Weighted- Average Remaining Contractual Term
Outstanding at December 31, 2013	4 years 125 days	[1],[2]	4 years 124 days
Granted	6 years 40 days
Outstanding at December 31, 2014	4 years 125 days	[1],[2]	4 years 124 days
Vested and exercisable at December 31, 2014	3 years 82 days	[1]

[1] At December 31, 2014, 0.8 million of these SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.

[2] At December 31, 2014, SARs outstanding had an intrinsic value of $58.5 million. SARs vested and exercisable had an intrinsic value of $30.8 million.