Subsequent Event Subsequent Event (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
Jun. 30, 2012	Dec. 31, 2011	Jul. 02, 2012
Subsequent Event
Gross written premiums written by Hardy		$ 430
Business Acquisition, Cost of Acquired Entity, Purchase Price			230
Business Combination, Acquisition Related Costs	4
Business Acquisition, Cost of Acquired Entity, Cash Paid			230
Acquired Indefinite-lived Intangible Asset, Amount			55
Acquired Finite-lived Intangible Asset, Amount			80
Business Acquisition, Purchase Price Allocation, Goodwill Amount			$ 35

Gross written premiums written by Hardy

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- Definition

The aggregate amount assigned to a major class of finite-lived intangible assets acquired either individually or as part of a group of assets (in either an asset acquisition or business combination). A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 44

-Subparagraph a(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

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- Definition

The aggregate cost of a major indefinite-lived intangible asset class acquired, during the period, either individually or as part of a group of assets (in either an asset acquisition or business combination).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 44

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6905858&loc=d3e16265-109275

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- Definition

Amount of cash paid to acquire the entity.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph f(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

+ Details

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- Definition

Amount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 52

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 53

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 59

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=6909708&loc=d3e1043-128460

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