Earnings Per Share (Comparison Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic earnings per share:
Net income	$ 153.4	$ 9.5	$ 227.5	$ 133.8
Weighted average common shares outstanding	88,742,484	92,441,730	89,495,564	94,178,989
Basic earnings per share	$ 1.73	$ 0.10	$ 2.54	$ 1.42
Diluted earnings per share:
Net income	$ 153.4	$ 9.5	$ 227.5	$ 133.8
Weighted average common shares outstanding	88,742,484	92,441,730	89,495,564	94,178,989
Share equivalents:
Warrants and options	829,584	1,075,735	832,432	1,102,252
RSUs and LTIP awards	443,336	452,938	479,038	534,653
Employee share purchase plan	25,105	13,823	23,780	14,561
Weighted average common shares and common share equivalents outstanding - diluted	90,040,509	93,984,226	90,830,814	95,830,455
Diluted earnings per share	$ 1.70	$ 0.10	$ 2.50	$ 1.40