Acquisition and Disposals - Allied - Acquisition Consideration (Narrative) (Details) - Allied International Holdings, Inc. - USD ($) $ in Millions	Mar. 31, 2017	Feb. 01, 2016	Apr. 11, 2017
Business Acquisition [Line Items]
Cash consideration		$ 75.7
Measurement period		3 years
Contingent consideration liability	$ 17.0	$ 15.0
Total acquisition consideration		90.7
Change in estimate of contingent considaration	$ 2.0
Fair value of net assets acquired and liabilities assumed		76.7
Indefinite-lived intangible assets acquired during the period		8.0
Finite-lived intangible assets acquired		6.0
Goodwill acquired during the period		14.1
Insurance Segment
Business Acquisition [Line Items]
Goodwill acquired during the period		$ 14.1
Subsequent Event [Member]
Business Acquisition [Line Items]
Contingent consideration, low end of range			$ 12.5
Contingent consideration, high end of range			$ 20.0