Income Taxes (Schedule of (Benefit) Provision for Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current U.S. federal income tax provision									$ 73.7	$ 0.3	$ 0.3
Deferred U.S. federal income tax (benefit) / provision									24.8	906.9	(566.3)
Total federal income tax (benefit) / provision									98.5	907.2	(566.0)
Current state and local income tax (benefit) / provision									(0.7)	14.6	5.8
Deferred state and local income tax (benefit) / provision									(27.8)	1.8	(21.0)
Total state and local income tax (benefit) / provision									(28.5)	16.4	(15.2)
Total non-U.S. income tax (benefit) / provision									(31.4)	90.8	82.4
Total Effective Tax Rate									38.6	1,014.4	(498.8)
Continuing operations (benefit) / provision	$ 27.7	$ (119.8)	$ (31.9)	$ 56.2	$ (6.6)	$ 54.5	$ 111.2	$ 44.4	(67.8)	203.5	(538.0)
Discontinued operations (benefit) / provision									$ 106.4	$ 810.9	$ 39.2