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Derivatives (Interest rate cap) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2014 Interest Rate Cap Rating	Dec. 31, 2013 Interest Rate Cap	May 31, 2007 Sirius International Group Ltd Preferred Stock	Mar. 31, 2014 Sirius International Group Ltd Interest Rate Cap	Mar. 31, 2014 Standard & Poor's, A Rating Barclays Interest Rate Cap	Mar. 31, 2014 Standard & Poor's, AA- Rating Nordea Bank Finland [Member] Interest Rate Cap
Derivative [Line Items]
Derivative Collateral Right to Reclaim	$ (8.2)				$ 5.7	$ 2.5
Preferred Stock, Dividend Rate, Percentage			7.506%
Term of LIBOR loan			3 months
Derivative, Cap Interest Rate				8.30%
Derivative, Cost of Hedge				9.9
basis points			3.20%	3.95%
Non-cumulative perpetual preference shares issued			250.0
years of interest rate cap				5 years
Derivative, fair value, net	8.2	11.1
Purchases	0
Realized and unrealized gains (losses)	(2.9)
Sales/settlements	$ 0
S and P Credit Ratings	21

X

- Definition

Cap rate on an interest rate derivative such as an interest rate cap or collar. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

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X

- Definition

The premium (cost) of a hedge, expensed during the period.

+ References

No definition available.

+ Details

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X

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB

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-Topic 820

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-Paragraph 2

-Subparagraph (c)(2)

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- Definition

The percentage rate used to calculate dividend payments on preferred stock.

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- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

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- Definition

basis points

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- Definition

The amount of collateral held against amounts due to counterparties for over the counter derivative instruments against net derivative instrument positions.

+ References

No definition available.

+ Details

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- Definition

Sales and settlements that have taken place during the period in relation to derivative assets measured at fair value on a recurring basis.

+ References

No definition available.

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- Definition

Represents the S&P creditworthiness heirarchy ratings used by the entity.

+ References

No definition available.

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- Definition

Term of LIBOR loan

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- Definition

Years of interest rate cap

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