Reinsurance (Summary of Reinsurance Activity) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Insurance [Abstract]
Net assumed written premiums	$ 12.9	$ 9.7	$ 43.3	$ 31.6
Net premiums earned	12.2	10.3	34.2	30.9
Provision for claims	7.0	5.5	19.5	17.6
Amortization of capitalized acquisition costs	$ 0.3	$ 0.3	$ 0.8	$ 0.8