Reinsurance (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Percentage of ceded earned premiums to gross earned premiums	38.00%	38.00%
Percentage of assumed earned premiums to net earned premiums	26.00%	25.00%
Program services and other [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance recoverables	$ 308.0	$ 365.0