Segment Information (Identifiable Assets by Business Segment) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Identifiable assets	$ 11,983.4	$ 12,399.7
Identifiable assets	103.6	103.9
Assets Held-for-Sale [Member]
Segment Reporting Information [Line Items]
Identifiable assets	23.6	57.4
Assets of Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable assets	103.6	103.9
U.S. Companies [Member]
Segment Reporting Information [Line Items]
Identifiable assets	$ 11,856.2	$ 12,238.4