Income Taxes (Details 3) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Deferred income tax assets related to:
Non-U.S. net operating loss carryforwards	$ 504.0	$ 545.4
Loss reserve discount	114.2	142.4
U.S. federal and state net operating loss carryforwards	102.7	103.6
Incentive compensation	43.4	36.9
Unearned premiums	41.2	37.3
U.S. tax credit carryforwards	13.5	12.0
Deferred compensation	11.4	13.1
Loss on sale of AutoOne	10.4
Pension and benefit accruals	8.0	4.3
Accrued interest	3.5	0.5
Investment basis differences	1.6	7.3
Fixed assets	(0.1)	4.8
Other items	9.5	14.1
Total gross deferred income tax assets	863.3	921.7
Less: valuation allowances	(232.7)	(385.8)
Total net deferred income tax assets	630.6	535.9
Deferred income tax liabilities related to:
Safety reserve	369.6	378.5
Deferred acquisition costs	48.8	41.5
Net unrealized investment gains	34.8	55.8
Purchase accounting	0.7	2.1
Intangible assets	(0.1)	0.1
Other items	5.4	(0.8)
Total deferred income tax liabilities	459.2	477.2
Net deferred tax asset (liability)	$ 171.4	$ 58.7