Incentive Compensation Plans Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based Payment Award
Intrinsic value of stock options exercised	$ 15.2	$ 16.1	$ 10.7
Proceeds from Stock Options Exercised including Taxes Withheld	$ 18.2	$ 20.4	$ 25.2
Employee Stock Option
Stock-based Payment Award
Stock options outstanding as of January 1, 2016	6.0
Stock options outstanding as of Jan 1, 2016, Weighted-average exercise price	$ 9.63
Exercised	(1.2)	(1.4)	(1.7)
Exercised, Weighted-average exercise price	$ 9.62
Stock options outstanding as of December 31, 2016	4.8	6.0
Stock options outstanding as of Dec 31, 2016, Weighted-average exercise price	$ 9.83	$ 9.63
Options outstanding, Weighted Average Remaining Contractual Term	3 years 1 month
Stock options outstanding, Aggregate intrinsic value	$ 61.0