Condensed Consolidated Statements of Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Earned premiums, from affiliates	$ 53.1	$ 81.2	$ 112.8	$ 179.2
Net investment income, from affiliate	0.4	1.2	1.6	2.4
Losses and loss expenses, from affiliates	50.0	37.0	100.9	93.2
Net Acquisition and Operating Expenses, from affiliates	12.7	35.7	36.9	79.1
Interest Expense Debt To Affiliates	$ 0.3	$ 0.3	$ 0.5	$ 0.5