Segment Information (Identifiable Assets by Business Segment) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Identifiable assets	$ 12,399.7	$ 15,469.6
Identifiable assets	57.4	4,466.6
Assets Held-for-Sale [Member]
Segment Reporting Information [Line Items]
Identifiable assets	57.4	4,466.6
Assets of Discontinued Life Business [Member]
Segment Reporting Information [Line Items]
Identifiable assets	103.9	88.0
U.S. Companies [Member]
Segment Reporting Information [Line Items]
Identifiable assets	$ 12,238.4	$ 10,915.0