Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding (Stock appreciation rights (SARs), USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015		Dec. 31, 2014
Stock appreciation rights (SARs)
SARs [Roll Forward]
Outstanding at December 31, 2014 (in shares)	1,400,000
Granted (in shares)	300,000
Outstanding at March 31, 2015 (in shares)	1,700,000	[1],[2]	1,400,000
Vested and exercisable at March 31, 2015 (in shares)	900,000	[1]
Per Share Weighted- Average Exercise Price [Roll Forward]
Outstanding at December 31, 2014 (in Dollars per share)	$ 44.44
Granted (in Dollars per share)	$ 77.92
Outstanding at March 31, 2015 (in Dollars per share)	$ 51.05	[1],[2]	$ 44.44
Vested and exercisable at March 31, 2015 (in Dollars per share)	$ 38.67	[1]
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2014 (in Dollars per share)	$ 13.26
Granted (in Dollars per share)	$ 17.56
Outstanding at March 31, 2015 (in Dollars per share)	$ 14.13	[1],[2]	$ 13.26
Vested and exercisable at March 31, 2015 (in Dollars per share)	$ 12.58	[1]
Weighted Average Remaining Contractual Term [Roll Forward]
Outstanding at December 31, 2014	4 years 5 months 82 days	[1],[2]	4 years 4 months 2 days
Granted	6 years 6 months 131 days
Outstanding at March 31, 2015	4 years 5 months 82 days	[1],[2]	4 years 4 months 2 days
Vested and exercisable at March 31, 2015	2 years 15 months 92 days	[1]

[1] Total SARs outstanding had an intrinsic value of $52.5 million. SARs vested and exercisable had an intrinsic value of $38.1 million.

[2] As of March 31, 2015, 0.8 million of the SARs outstanding were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.