v2.4.0.6

Basis of Reporting - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified | 3 Months Ended | 9 Months Ended |  |  |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2012 | Sep. 30, 2011 | Sep. 30, 2012 | Sep. 30, 2011 | Sep. 30, 2012 ACAC | Aug. 31, 2011 ACAC | Sep. 30, 2012 Tiger and AMT Alpha | Sep. 30, 2012 Tiger and AMT Alpha ACAC | Sep. 30, 2011 Restatement Adjustment Majestic | Sep. 30, 2011 Restatement Adjustment Majestic
Subsidiary of Limited Liability Company or Limited Partnership [Line Items] |  |  |  |  |  |  |  |  |  |
Retrospective gain, pretax |  |  |  |  |  |  |  |  | $ 3,185 | $ 3,185
Retrospective gain, after tax |  |  |  |  |  |  |  |  | 2,070 | 2,070
Impact on diluted earnings per share in both periods |  |  |  |  |  |  |  |  | $ 0.03 | $ 0.03
Percentage of stock dividend paid | 10.00% |  |  |  |  |  |  |  |  |
Impact of dividends declared on earnings per share |  | $ (0.02) |  | $ (0.02) |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  | 21.25% | 21.25% | 50.00% | 50.00% |  |
Profits and losses of investment in life insurance policies and premium finance loans |  |  | 60.625% |  |  |  |  |  |  |
Income and losses attributable to indirect ownership as a component of Equity in Earnings of Unconsolidated Subsidiaries |  |  |  |  |  |  | 10.625% |  |  |
Decrease in Equity Investment in Subsidiary |  |  | $ 3,807 |  |  |  |  |  |  |

X
- Definition Equity Method Investment, Percentage Of Earnings + References No definition available. + Details
Name: | afsi_EquityMethodInvestmentPercentageOfEarnings
Namespace Prefix: | afsi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Impact of Dividends Declared on Earning Per Share + References No definition available. + Details
Name: | afsi_ImpactOfDividendsDeclaredOnEarningPerShare
Namespace Prefix: | afsi_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Increase Decrease In Assets of Equity Method Investment + References No definition available. + Details
Name: | afsi_IncreaseDecreaseInAssetsOfEquityMethodInvestment
Namespace Prefix: | afsi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage Of Ownership Interests + References No definition available. + Details
Name: | afsi_PercentageOfOwnershipInterests
Namespace Prefix: | afsi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Stock Dividend Paid, Percentage + References No definition available. + Details
Name: | afsi_StockDividendPaidPercentage
Namespace Prefix: | afsi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Per share amount effect of a restatement of results of operations on diluted earnings per share. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 154 -Paragraph 17, 18, 26 -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 Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=16381557&loc=d3e3842-109258 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22644-107794 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 57, 58 -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
Name: | us-gaap_ImpactOfRestatementOnEarningsPerShareDiluted
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Pre-tax adjustment in the annual report for the year in which a restatement is made, of the resulting effects on the net income of prior periods on the beginning balance of retained earnings for the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22644-107794 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 9 -Paragraph 26 -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 250 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22663-107794 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22658-107794 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 154 -Paragraph 17, 18, 26 -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
Name: | us-gaap_ImpactOfRestatementOnOpeningRetainedEarningsBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Net of tax adjustment in the annual report for the year in which a restatement is made, of the resulting effects on the net income of prior periods on the beginning balance of retained earnings for the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22644-107794 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 9 -Paragraph 26 -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 250 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22663-107794 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22658-107794 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 154 -Paragraph 17, 18, 26 -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
Name: | us-gaap_ImpactOfRestatementOnOpeningRetainedEarningsNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Life insurance assumed from another insurer divided by gross life insurance in force. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 05 -Paragraph c -Article 7 + Details
Name: | us-gaap_LifeInsuranceAssumedRatio
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_SubsidiaryOfLimitedLiabilityCompanyOrLimitedPartnershipLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration