Equity - Share Repurchases, Dividends, Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Jul. 25, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share Repurchase Plan
Number of shares authorized by the Board of Directors to be repurchased under share repurchase plan		8,400,000		8,400,000
Number of shares authorized by the Board of Directors to be repurchased under share repurchase plan, expressed as a percentage of outstanding shares (as a percent)		12.00%		12.00%
Number of shares repurchased under stock repurchase plan				0
Dividends
Common stock quarterly dividend per share (in dollars per share)	$ 0.45
Common stock dividend quarterly declared and paid per share (in dollars per share)		$ 0.45	$ 0.40	$ 0.90	$ 0.80
Dividends paid		$ 32.8	$ 29.0	$ 65.6	$ 57.1
Changes restricted stock grants and RSUs
Unvested at the beginning of the period (in shares)				985,540
Granted (in shares)				446,525
Vested (in shares)				(6,029)
Cancelled (in shares)				(31,901)
Unvested at the end of the period (in shares)		1,394,135		1,394,135
Shares reserved for future grants (all plans)		1,643,169		1,643,169
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)				$ 64.34
Granted (in dollars per shares)				79.60
Vested (in dollars per shares)				61.86
Cancelled (in dollars per shares)				67.40
Unvested at the end of the period (in dollars per shares)		$ 69.17		$ 69.17
Common Stock Including Additional Paid in Capital
Common Stock and Additional Paid-In (in Shares)
Stock-based compensation ( in shares)		20,794		162,302
Stock options exercised (in shares)		1,225		56,530
Total ( in shares)		22,019		218,832
Stock-based compensation expense				$ 14.9
Payments made to tax authorities on employees' behalf				0.7
Common Stock and Additional Paid-In (in Amount)
Stock-based compensation		$ 9.4		14.2
Stock options exercised				2.8
Total		$ 9.4		$ 17.0
Weighted Average Exercise/(Purchase) Price
Stock options exercised (in dollars per share)		$ 55.73		$ 49.95
Restricted stock | Immediately Vested
Changes restricted stock grants and RSUs
Granted (in shares)		18,120
Weighted Average Grant Date Fair Value
Granted (in dollars per shares)		$ 71.73
RSU's
Dividends
Dividend equivalents				$ 0.9	$ 0.9
Stock-Based Compensation
Vesting period (in years)				3 years
Changes restricted stock grants and RSUs
Granted (in shares)				446,525
RSU's | Performance-based
Changes restricted stock grants and RSUs
Granted (in shares)				169,009