v2.4.0.6

Results of Operations Related to Reinsurance Agreements (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2012 | Sep. 30, 2011 | Sep. 30, 2012 | Sep. 30, 2011
Related Party Transaction [Line Items] |  |  |  |
Change in unearned premium - ceded | $ (96,212) | $ (33,055) | $ (199,560) | $ (194,135)
Incurred loss and loss adjustment expense - ceded | 255,646 | 185,352 | 667,362 | 484,056
Related Party Transactions |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Premium written - ceded | (189,655) | (173,218) | (576,936) | (513,859)
Change in unearned premium - ceded | 10,541 | 13,008 | 61,502 | 103,022
Earned premium - ceded | (179,114) | (160,210) | (515,434) | (410,837)
Ceding commission on premium written | 51,955 | 48,339 | 157,224 | 132,224
Ceding commission - deferred | (2,095) | (6,557) | (16,540) | (20,269)
Ceding commission - earned | 49,860 | 41,782 | 140,684 | 111,955
Incurred loss and loss adjustment expense - ceded | $ 158,646 | $ 94,371 | $ 407,426 | $ 275,434

X
- Definition Ceded Premiums Earned + References No definition available. + Details
Name: | afsi_CededPremiumsEarned
Namespace Prefix: | afsi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Ceding Commission Deferred Net + References No definition available. + Details
Name: | afsi_CedingCommissionDeferredNet
Namespace Prefix: | afsi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Ceding Commission Earned + References No definition available. + Details
Name: | afsi_CedingCommissionEarned
Namespace Prefix: | afsi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Ceding Commission on Premium Written + References No definition available. + Details
Name: | afsi_CedingCommissionOnPremiumWritten
Namespace Prefix: | afsi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Total consideration paid and payable to reinsurers during the period pursuant to terms of reinsurance arrangements. + 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 FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -Subparagraph a, 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. + Details
Name: | us-gaap_CededPremiumsWritten
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Premiums recognized as revenue in the period earned on all types of insurance and reinsurance contracts not otherwise specified in the taxonomy after subtracting any amounts ceded to another insurer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -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 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
Name: | us-gaap_OtherPremiumRevenueNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Provision for benefits, claims and claims settlement expenses incurred during the period net of the effects of contracts assumed and ceded. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 + Details
Name: | us-gaap_PolicyholderBenefitsAndClaimsIncurredNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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