Condensed Consolidated Statements of Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Earned premiums, from affiliates	$ 114.8	$ 113.4
Net investment income, from affiliate	1.2	1.2
Losses and loss expenses, from affiliates	86.2	93.7
Net Acquisition and Operating Expenses, from affiliates	80.3	70.6
Interest Expense Debt To Affiliates	$ 0.2	$ 0.2