Retrocession Arrangements and Reinsurance Ceded Receivables (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Ceded Credit Risk [Line Items]
Reinsurance Claims Recoverables	$ 211.4	$ 143.0
Claims Recoverable From Retrocessionaires Past Due	$ 11.7	$ 10.9
AM Best, A- Rating [Member]
Ceded Credit Risk [Line Items]
Ceded Credit Risk, Disclosure	“A- (excellent)”	“A- (excellent)”