Reinsurance (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Percentage of ceded earned premiums to gross earned premiums	38.00%	36.00%
Percentage of assumed earned premiums to net earned premiums	25.00%	29.00%
Reinsurance recoverables	$ 134.0	$ 171.8
Program Services [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance recoverables	$ 365.0	$ 256.3