Business Segment Information (Geographic Region) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total Assets	$ 49,278.7	$ 64,170.2	$ 67,391.9
Total Revenue from continuing operations	3,207.2	3,093.7	2,612.9
Income (Loss) from continuing operations before provision (benefit) for income taxes	191.6	20.9	186.0
Income (loss) from continuing operations before attribution of noncontrolling interests	259.4	(182.6)	724.0
Assets of discontinued operations	501.3	13,220.7	13,059.6
U.S.
Segment Reporting Information [Line Items]
Total Assets	46,825.9	53,252.9	55,491.1
Total Revenue from continuing operations	3,046.1	2,755.6	2,084.5
Income (Loss) from continuing operations before provision (benefit) for income taxes	251.9	157.5	227.6
Income (loss) from continuing operations before attribution of noncontrolling interests	287.3	99.3	876.7
Europe
Segment Reporting Information [Line Items]
Total Assets	1,424.0	8,575.7	8,351.8
Total Revenue from continuing operations	119.6	139.7	125.0
Income (Loss) from continuing operations before provision (benefit) for income taxes	(34.5)	(189.2)	(227.6)
Income (loss) from continuing operations before attribution of noncontrolling interests	(19.8)	(246.8)	(304.6)
Other foreign
Segment Reporting Information [Line Items]
Total Assets	1,028.8	2,341.6	3,549.0
Total Revenue from continuing operations	41.5	198.4	403.4
Income (Loss) from continuing operations before provision (benefit) for income taxes	(25.8)	52.6	186.0
Income (loss) from continuing operations before attribution of noncontrolling interests	$ (8.1)	$ (35.1)	$ 151.9