Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Taxes
Effective tax rates (as a percent)	36.60%	(40.60%)	34.40%	33.50%
U.S. statutory rate (as a percent)	35.00%	35.00%	35.00%	35.00%
Foreign tax credit carryforwards	$ 20.6		$ 20.6
Net operating loss carryforwards for OBH	21.1		21.1
Expected decrease in unrecognized tax benefits upon completion of the Runoff Transaction			$ 11.5

The tax effect as of the balance sheet date of the amount of future tax effects arising from unused foreign tax credit carryforwards which will decrease future taxable income if applied in future years; a tax credit carryforward is the amount by which tax credits available for utilization exceeded statutory limits on inclusion in historical filings, and which can only be utilized if sufficient tax-basis income is generated in future periods and providing tax laws continue to allow such utilization.

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- Definition

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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- Definition

The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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OneBeacon U.S. Holdings, Inc. 10-Q