Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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No definition available.

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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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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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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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No definition available.

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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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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 (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Debt (Details) - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	May 12, 2017	Dec. 31, 2016	Jul. 23, 2015	Aug. 14, 2013
Debt Instrument
Total debt	$ 10.6	$ 10.6			$ 12.7
Draw down of debt and revolving line of credit		11.0	$ 102.5
Repayments of debt		13.3	$ 150.5
WTM Bank Facility
Debt Instrument
Total commitment under revolving credit facility							$ 425.0
White Mountains \| WTM Bank Facility
Debt Instrument
Total debt	0.0	0.0			0.0
MediaAlpha \| MediaAlpha Bank Facility
Debt Instrument
Unamortized issuance cost	0.0	0.0
Debt instrument at face value	$ 10.6	$ 10.6
Debt instrument, interest rate, effective percentage	5.40%	5.40%
Line of credit facility, fair value of amount outstanding	$ 10.6	$ 10.6
Total commitment under revolving credit facility				$ 20.0
Remaining borrowing capacity	15.0	15.0
Long-term line of credit	6.0	6.0
Proceeds from issuance of debt	11.0	11.0
Draw down of debt and revolving line of credit	6.0	6.0
MediaAlpha \| Previous MediaAlpha Bank Facility
Debt Instrument
Unamortized issuance cost	0.0	0.0			(0.2)
Debt instrument at face value	0.0	0.0			$ 12.9
Debt instrument, interest rate, effective percentage					5.70%
Line of credit facility, fair value of amount outstanding	0.0	0.0			$ 12.7
Total commitment under revolving credit facility						$ 20.0
Repayments of debt	11.7	12.9
OneBeacon \| 2012 OBH Senior Notes
Debt Instrument
Total debt	0.0	0.0			0.0
Unamortized issuance cost	0.0	$ 0.0			$ 0.0
Term Loan \| MediaAlpha Bank Facility
Debt Instrument
Basis points		1.50%
Term Loan \| MediaAlpha \| MediaAlpha Bank Facility
Debt Instrument
Debt instrument at face value	4.6	$ 4.6
Notional amount	5.0	5.0
Proceeds from issuance of debt	5.0	5.0
Repayments of debt	$ 0.4	$ 0.4
Line of Credit \| MediaAlpha Bank Facility
Debt Instrument
Basis points		0.25%