Equity - Share Repurchases, Dividends, Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Apr. 19, 2016	Jan. 01, 2016	Mar. 31, 2016	Mar. 31, 2015
Share Repurchase Plan
Number of shares authorized by the Board of Directors to be repurchased under share repurchase plan			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%
Number of shares repurchased under stock repurchase plan			0
Common Stock and Additional Paid-In (in Shares)
Repurchase of common shares (in shares)			0
Dividends
Common stock dividend quarterly declared and paid per share (in dollars per share)			$ 0.40	$ 0.40
Dividends paid			$ 28.9	$ 30.7
Changes in unvested restricted stock grants and RSUs
Unvested at the beginning of the period (in shares)		900,410	900,410
Granted (in shares)			512,895
Vested (in shares)			(256)
Canceled (in shares)			(5,684)
Unvested at the end of the period (in shares)			1,407,365
Shares reserved for future grants (all plans)			1,859,259
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)		$ 63.26	$ 63.26
Granted (in dollars per shares)			69.16
Vested (in dollars per shares)			59.27
Canceled (in dollars per shares)			65.96
Unvested at the end of the period (in dollars per shares)			$ 65.40
Subsequent event
Dividends
Common stock quarterly dividend per share (in dollars per share)	$ 0.40
Early Adoption | Improvements to Employee Share-Based Payment Accounting
Stock-Based Compensation
Cumulative-effect adjustment		$ 0.6
Common Stock Including Additional Paid in Capital
Common Stock and Additional Paid-In (in Shares)
Stock options exercised (in shares)			345,170
Total ( in shares)			345,170
Common Stock and Additional Paid-In (in Amount)
Stock-based compensation			$ 2.1
Stock options exercised			16.5
Cumulative effect of change in accounting for stock-based compensation			1.0
Total			$ 19.6
Weighted Average Exercise/(Purchase) Price
Stock options exercised (in dollars per share)			$ 64.87
RSU's
Dividends
Dividend equivalents			$ 0.9	$ 1.0
Stock-Based Compensation
Vesting period (in years)			3 years
Changes in unvested restricted stock grants and RSUs
Granted (in shares)			512,895
RSU's | Performance-based
Changes in unvested restricted stock grants and RSUs
Granted (in shares)			190,175