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Acquisitions - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |  |  | 9 Months Ended |
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Sep. 30, 2012 Cnh Capital Insurance Agencies | Jul. 12, 2012 Cnh Capital Insurance Agencies | Dec. 31, 2011 Builders and Trades Men's Insurance Services Inc | Sep. 30, 2012 Builders and Trades Men's Insurance Services Inc | Sep. 30, 2012 Builders and Trades Men's Insurance Services Inc | Dec. 31, 2011 Builders and Trades Men's Insurance Services Inc Renewal Rights | Dec. 31, 2011 Builders and Trades Men's Insurance Services Inc Distribution Networks | Sep. 30, 2012 Majestic | Sep. 30, 2012 Majestic | Sep. 30, 2011 Majestic | Jun. 01, 2011 Majestic | Sep. 30, 2012 Majestic Distribution Networks and Trademarks | Sep. 30, 2012 Majestic Distribution Networks | Sep. 30, 2012 Majestic Trademarks | Sep. 30, 2011 Majestic Maximum
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of acquisition |  | $ 34,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Preliminary purchase price recorded by the company |  | 34,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Assigned to intangible assets |  | 33,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Advance payment made for acquisition |  |  | 5,000 |  |  |  |  |  |  |  |  |  |  |  |
Business acquisition profitability measurement period |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |
Business acquisition, purchase price |  |  | 47,000 |  |  |  |  |  |  |  |  |  |  |  |
Business acquisition, goodwill and intangibles |  |  | 59,000 |  |  |  |  |  |  |  |  |  |  |  |
Acquired finite-lived intangible assets, weighted average useful life |  |  |  |  |  | 11 years | 17 years |  |  |  |  |  | 13 years | 2 years |
Liability related to an unfavorable lease assumed |  |  | 2,400 |  |  |  |  | 390 | 390 |  |  |  |  |  |
Fee revenue recorded during acquisition |  |  |  | 3,600 | 14,600 |  |  |  |  |  |  |  |  |  |
Liability for losses and loss adjustment expenses gross |  |  |  |  |  |  |  |  |  | 331,660 |  |  |  |  |
Percentage of unearned premium reserve assumed |  |  |  |  |  |  |  |  |  | 100.00% |  |  |  |  |
Unearned premium reserve amount assumed |  |  |  |  |  |  |  |  |  | 25,997 |  |  |  |  |
Cash and investments received |  |  |  |  |  |  |  |  |  | 224,532 |  |  |  |  |
Reserve deficiency |  |  |  |  |  |  |  |  |  | 26,000 |  |  |  |  |
Reinsurance recoverable |  |  |  |  |  |  |  |  |  | 51,715 |  |  |  |  |
Percentage of net earned premium paid to acquiree |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.00%
Required loss ratio in the three year period commencing on the losing date |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65.00%
Insurance premiums recorded since acquisition date | 4,400 |  |  | 24,000 | 52,000 |  |  | 26,000 | 73,500 |  |  |  |  |  |
Acquired finite-lived intangible assets |  |  |  |  |  |  |  |  |  |  |  | 3,870 |  |  |
Liability related to profit sharing provision |  |  |  |  |  |  |  | 815 | 815 |  |  |  |  |  |
Fair value of loss reserve |  |  |  |  |  |  |  |  |  |  | $ 328,905 |  |  |  |

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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 Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16265-109275 Reference 2: 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. + Details
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- Definition Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16265-109275 + Details
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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 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. + Details
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- Definition The amount of acquisition cost of a business combination allocated to unfavorable contracts assumed from the acquired entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141 -Paragraph 37 -Subparagraph k -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 Emerging Issues Task Force (EITF) -Number 04-1 -Paragraph 4, 8 -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. + Details
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- Definition This element represents the acquisition-date fair value of the total consideration transferred which consists of the sum of the acquisition-date fair values of the assets transferred by the acquirer, the liabilities incurred by the acquirer to former owners of the acquiree, and the equity interests issued by the acquirer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141R -Paragraph 68 -Subparagraph f -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 141R -Paragraph 39, 40 -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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7488404&loc=d3e6927-128479 + Details
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- Definition This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period. + 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 (h)(1) -URI http://asc.fasb.org/extlink&oid=7659399&loc=d3e1392-128463 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141R -Paragraph 68 -Subparagraph r(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. + Details
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- Definition Net amount recognized for aggregate assets, including goodwill, in excess of or less than the aggregate liabilities assumed (also referred to as net assets acquired). This amount may also be viewed as incremental amount of equity that the consolidated entity (including the portion attributable to a noncontrolling interest) will recognize as a result of the business combination. + References No definition available. + Details
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