Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding - Stock appreciation rights (SARs) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		6 Months Ended		12 Months Ended
		Jun. 30, 2015		Dec. 31, 2014
SARs [Roll Forward]
Outstanding at December 31, 2014 (in shares)		1.4
Granted (in shares)		0.3
Exercised (in shares)		0.2
Outstanding at June 30, 2015 (in shares)		1.5	[1],[2]	1.4
Vested and exercisable at March 31, 2015 (in shares)	[2]	0.7
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
Exercised (in Dollars per share)		36.41
Outstanding at June 30, 2015 (in Dollars per share)		53.37	[1],[2]	$ 44.44
Vested and exercisable at March 31, 2015 (in Dollars per share)	[2]	39.38
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
Exercised (in Dollars per share)		12.60
Outstanding at June 30, 2015 (in Dollars per share)		14.34	[1],[2]	$ 13.26
Vested and exercisable at March 31, 2015 (in Dollars per share)	[2]	$ 12.48
Weighted Average Remaining Contractual Term [Roll Forward]
ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms		4 years 7 months 28 days	[1],[2]	4 years 4 months 2 days
Granted		6 years 7 months 10 days
ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms		4 years 7 months 28 days	[1],[2]	4 years 4 months 2 days
Vested and exercisable at March 31, 2015	[2]	3 years 5 months 9 days
Aggregate Intrinsic value of outstanding shares		$ 48.2
Aggregate intrinsic value of shares vested and exercisable		$ 30.2
Unvested
SARs [Roll Forward]
Outstanding at June 30, 2015 (in shares)		0.8

[1] As of June 30, 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

[2] Total SARs outstanding had an intrinsic value of $48.2 million. SARs vested and exercisable had an intrinsic value of $30.2 million