Condensed Consolidated Statements of Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Earned premiums, from affiliates	$ 58.3	$ 59.7
Net investment income, from affiliate	0.7	1.2
Losses and loss expenses, from affiliates	10.9	56.4
Net Acquisition and Operating Expenses, from affiliates	20.9	24.2
Interest Expense Debt To Affiliates	$ 0.2	$ 0.2