Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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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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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Fair value of the amount outstanding under the credit facility.

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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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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Debt and Standby Letter of Credit Facilities (Debt Outstanding) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Oct. 10, 2014	Aug. 14, 2013
Debt Instrument
Debt	$ 442.4	$ 343.1
Interest expense on debt	18.6	15.6	$ 16.2
Draw down of debt and revolving line of credit	195.5	133.6	200.0
WTM Bank Facility
Debt Instrument
Total commitment under revolving credit facility					$ 425.0
Line of Credit Facility, Fair Value of Amount Outstanding	50.0
Interest expense on debt	0.1	0.3	$ 0.3
Draw down of debt and revolving line of credit	125.0	65.0
Repayments of lines of credit	$ 75.0	$ 65.0
Effective yield (as a percent)	3.74%	3.65%
Prior W T M Bank Facility
Debt Instrument
Total commitment under revolving credit facility					$ 375.0
Other Debt [Member]
Debt Instrument
Debt	$ 0.0	$ 1.0
OneBeacon \| 2012 OBH Senior Notes
Debt Instrument
Debt instrument at face value	275.0	275.0
Unamortized original issue discount	(0.2)	(0.3)
Debt	274.8	274.7
White Mountains \| WTM Bank Facility
Debt Instrument
Debt	50.0	0.0
Tranzact [Member] \| Tranzact Bank Facility
Debt Instrument
Total commitment under revolving credit facility	116.0
Debt		67.4
Line of Credit Facility, Fair Value of Amount Outstanding	104.7			$ 70.0
Interest expense on debt	4.0	0.7
Line of Credit Facility, Amount Outstanding	104.7	68.7
Unamortized Debt Issuance Expense	(1.8)	(1.3)
Draw down of debt and revolving line of credit	24.0
Repayments of lines of credit	13.0
MediaAlpha [Member] \| MediaAlpha Bank Facility [Member]
Debt Instrument
Total commitment under revolving credit facility	20.0
Line of Credit Facility, Fair Value of Amount Outstanding		0.0
Line of Credit Facility, Amount Outstanding	15.0
Unamortized Debt Issuance Expense	(0.3)	0.0
Carrying Value \| OneBeacon \| 2012 OBH Senior Notes
Debt Instrument
Debt	274.8	274.7
Carrying Value \| Tranzact [Member] \| Tranzact Bank Facility
Debt Instrument
Debt	102.9	$ 67.4
Carrying Value \| MediaAlpha [Member] \| MediaAlpha Bank Facility [Member]
Debt Instrument
Debt	$ 14.7