Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that may be purchased by eligible participants (in shares)	0.9
Weighted Average Remaining Contractual Term [Roll Forward]
Proceeds from stock plans	$ 3.0	$ 2.6
Restricted stock units (RSUs)
SARs [Roll Forward]
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	0.5
Outstanding at March 31, 2017 (in shares)	1.3		1.3
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share)	$ 73.19
Granted (in dollars per share)	99.14
Outstanding at March 31, 2017 (in dollars per share)	$ 84.40		$ 73.19
Weighted Average Remaining Contractual Term [Roll Forward]
Outstanding at March 31, 2017	1 year 9 months 18 days
Stock appreciation rights (SARs)
SARs [Roll Forward]
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	0.3
Exercised (in shares)	0.0
Outstanding at March 31, 2017 (in shares)	1.6		1.3
Vested and exercisable at March 31, 2017 (in shares)	0.8
Per Share Weighted- Average Exercise Price [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share)	$ 66.22
Granted (in dollars per share)	99.07
Exercised (in dollars per share)	0.00
Outstanding at March 31, 2017 (in dollars per share)	73.16		$ 66.22
Vested and exercisable at March 31, 2017 (in dollars per share)	60.70
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share)	15.77
Granted (in dollars per share)	22.02
Exercised (in dollars per share)	0.00
Outstanding at March 31, 2017 (in dollars per share)	17.02		$ 15.77
Vested and exercisable at March 31, 2017 (in dollars per share)	$ 15.36
Weighted Average Remaining Contractual Term [Roll Forward]
Granted	6 years 10 months 6 days
Outstanding at March 31, 2017	4 years 9 months 11 days		4 years 4 months 24 days
Vested and exercisable at March 31, 2017	3 years 8 months 1 day
Aggregate Intrinsic value of outstanding shares	$ 54.2
Aggregate intrinsic value of shares vested and exercisable	$ 36.4
Stock appreciation rights (SARs) | Unvested
SARs [Roll Forward]
Outstanding at March 31, 2017 (in shares)	0.8
Executive officer | Restricted stock units (RSUs)
SARs [Roll Forward]
Granted (in shares)	0.2
Target amount | Executive officer | Minimum | Restricted stock units (RSUs)
SARs [Roll Forward]
Percentage of shares authorized for grant	0.00%
Target amount | Executive officer | Maximum | Restricted stock units (RSUs)
SARs [Roll Forward]
Percentage of shares authorized for grant	200.00%