Reinsurance (Summary of Reinsurance Activity) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Insurance [Abstract]
Net assumed written premiums	$ 14.2	$ 9.6	$ 30.4	$ 21.9
Net premiums earned	11.7	10.5	22.0	20.6
Provision for claims	7.3	6.1	12.5	12.1
Amortization of capitalized acquisition costs	$ 0.2	$ 0.2	$ 0.5	$ 0.5