Investments (Schedule Of Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net Investment Income [Line Items]
Net investment income	$ 53.3	$ 44.6
Fixed maturity investments
Net Investment Income [Line Items]
Net investment income	48.0	36.2
Equity securities
Net Investment Income [Line Items]
Net investment income	1.8	3.6
Other invested assets: hedge funds and private equity
Net Investment Income [Line Items]
Net investment income	4.7	8.4
Other invested assets: other private securities
Net Investment Income [Line Items]
Net investment income	3.1	0.9
Cash and cash equivalents
Net Investment Income [Line Items]
Net investment income	0.5	0.5
Expenses
Net Investment Income [Line Items]
Net investment income	$ (4.8)	$ (5.0)