Acquisitions (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Business Acquisition [Line Items]
Goodwill	$ 35,068
Intangible assets	26,903
Business acquisition, intangible assets amortized period, years	7 years
Heartland Crop Insurance, Inc [Member]
Business Acquisition [Line Items]
Business acquisition date	Jan. 02, 2011
Business acquisition cash paid	$ 55,000
Premiere Underwriting Services [Member]
Business Acquisition [Line Items]
Business acquisition date	Jan. 28, 2011
Executive Risk Insurance Services, Ltd [Member]
Business Acquisition [Line Items]
Business acquisition date	Jan. 31, 2011

Business acquisition, intangible assets amortized period.

No definition available.

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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

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- Definition

Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Acquisition Date

-URI http://asc.fasb.org/extlink&oid=6919109

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-Publisher FASB

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- Definition

The amount of acquisition cost of a business combination allocated to an identifiable intangible asset that will be amortized.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 141

-Paragraph 52

-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

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)

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-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.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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