Share-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock			63,255
Restricted Stock Units expected to vest			1,370,435
Share Based Compensation Restricted Stock Value			$ 2.7
Share Based Compensation Restricted Stock Units Aggregate Intrinsic Value			$ 59.0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price			$ 25.03
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	5 years 6 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value			$ 26.9
Restricted Stock Units Outstanding	1,798,543	1,769,420	2,047,158	1,798,543	1,769,420	1,522,038
Weighted Average Grant Price of Restricted Stock Forfeited			$ 26.28	$ 27.17	$ 25.48
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 27.30	$ 31.60	$ 26.44	$ 27.30	$ 31.60	$ 35.54
Stock Options without a fixed expiration date			21,252
Total shares authorized under stock option and incentive plan			9,000,000
Number of shares available for future grants of stock options or restricted stock			5,685,169
Compensation expense not yet recognized for nonvested share-based awards			$ 25.7
Nonvested share-based awards, expected weighted average period to be recognized, years	2 years 3 months 18 days
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options			1.5	$ 0.8	$ 0.4
Total intrinsic value of stock options exercised			10.0	6.7	3.9
Cash received from the exercise of stock options			23.8	22.7	$ 10.6
Aggregate intrinsic value of outstanding stock options	$ 8.0		58.9	8.0
Aggregate intrinsic value of exercisable options	$ 8.0		$ 31.0	$ 8.0
Outstanding stock options, Weighted average remaining contractual life (years)	3 years	3 years 36 days	4 years 1 month 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number			1,491,656
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	3,804,095	5,630,502	3,437,910	3,804,095	5,630,502	5,874,590
Total fair value of restricted stock vesting			$ 19.4		$ 15.2
Weighted average issue price			$ 24.43	$ 29.02	$ 28.87
Total fair value granted			$ 19.4		$ 15.2
Stock Issued During Period, Shares, Restricted Stock Award, Gross			36,594	22,441	16,670
Restricted Stock Units Granted			1,033,167	790,929	727,300
Weighted Average Grant Price of Restricted Stock Units Granted			$ 21.69	$ 29.06	$ 28.81
Restricted Stock Units Vested			(724,713)	(673,385)	(416,755)
Weighted Average Grant Price of Restricted Stock Units Vested			$ 25.88	$ 24.78	$ 22.26
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award, Gross					16,670
Restricted Stock Units Granted			32,310	31,080	6,656