Contingencies (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended	54 Months Ended
	Jun. 30, 2007	Mar. 31, 2016	Mar. 31, 2015	Jun. 30, 2014	Sep. 30, 2015	Mar. 31, 2016	Oct. 07, 2011
Loss Contingencies [Line Items]
Net gain on sale of discontinued operations		$ 0.0	$ 8.0
Esurance
Loss Contingencies [Line Items]
Percentage of fluctuation in loss reserves of transferred subsidiaries retained							90.00%
Tribune Company Litigation | Pending Litigation | OneBeacon [Member]
Loss Contingencies [Line Items]
Proceeds from Sale, Maturity and Collection of Investments	$ 32.0
Discontinued Operations [Member]
Loss Contingencies [Line Items]
Net gain on sale of discontinued operations		(0.9)	65.9	$ 2.7
Esurance | Discontinued Operations [Member]
Loss Contingencies [Line Items]
Net gain on sale of discontinued operations		0.0	8.0		$ 10.3	$ 28.3
OneBeacon Runoff [Member] | Discontinued Operations [Member]
Loss Contingencies [Line Items]
Net gain on sale of discontinued operations		0.0	(0.1)
Sirius Group | Discontinued Operations [Member]
Loss Contingencies [Line Items]
Net gain on sale of discontinued operations		$ (0.9)	$ 65.9