Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding - Stock appreciation rights (SARs) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2014
SARs [Roll Forward]
Outstanding at December 31, 2014 (in shares)	1.3
Granted (in shares)	0.4
Exercised (in shares)	0.0
Outstanding at September 30, 2015 (in shares)	1.7
Vested and exercisable at September 30, 2015 (in shares)	0.9
Per Share Weighted- Average Exercise Price [Roll Forward]
Outstanding at December 31, 2014 (in Dollars per share)	$ 56.47
Granted (in Dollars per share)	80.06
Exercised (in Dollars per share)	0.00
Outstanding at September 30, 2015 (in Dollars per share)	61.31
Vested and exercisable at September 30, 2015 (in Dollars per share)	49.80
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2014 (in Dollars per share)	14.92
Granted (in Dollars per share)	16.50
Exercised (in Dollars per share)	0.00
Outstanding at September 30, 2015 (in Dollars per share)	15.24
Vested and exercisable at September 30, 2015 (in Dollars per share)	$ 14.21
Weighted Average Remaining Contractual Term [Roll Forward]
Granted	6 years 10 months 10 days
Outstanding at September 30, 2015	4 years 7 months 17 days	4 years 5 months 16 days
Vested and exercisable at September 30, 2015	3 years 5 months 5 days
Aggregate Intrinsic value of outstanding shares	$ 46.6
Aggregate intrinsic value of shares vested and exercisable	$ 34.2
Unvested
SARs [Roll Forward]
Outstanding at September 30, 2015 (in shares)	0.8