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Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 OBH Senior Notes	Dec. 31, 2011 OBH Senior Notes	Mar. 31, 2012 SIG Senior Notes	Dec. 31, 2011 SIG Senior Notes	Mar. 31, 2012 Old Lyme	Dec. 31, 2011 Old Lyme	Dec. 30, 2011 Old Lyme Y	Aug. 12, 2011 WTM Bank Facility	Mar. 31, 2012 Other debt	Dec. 31, 2011 Other debt
Debt Instrument
Debt instrument at face value			$ 269.9	$ 269.9	$ 400.0	$ 400.0
Unamortized original issue discount			(0.1)	(0.1)	(0.7)	(0.7)
Total debt	677.2	677.5	269.8	269.8	399.3	399.3	2.1	2.1	2.1		6.0	6.3
Total commitment under revolving credit facility										375.0
Debt Instrument Term (in years)									5
Percentage of principal amount of debt subject to upward or downward adjustments									50.00%
Principal amount of purchase note									$ 6.0

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- Definition

Amount of cash paid to acquire the entity.

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The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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