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Commitments and Contingencies - Fair Value of Annuities (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014
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Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | $ 94,561 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus
Metropolitan Life Insurance Company (A+) [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | 15,451 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_MetropolitanLifeInsuranceCompanyMember
American General Life Insurance (A) [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | 15,432 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_AmericanGeneralLifeInsuranceMember
Pacific Life and Annuity Company (A+) [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | 15,306 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_PacificLifeAndAnnuityCompanyMember
New York Life Insurance Company (A++) [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | 12,131 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_NewYorkLifeInsuranceCompanyMember
John Hancock Life Insurance Company USA (A+) [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | 7,854 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_JohnHancockLifeInsuranceCompanyUsaMember
Athene Annuity and Life Assurance Company (B++) [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | 6,543 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_AtheneAnnuityAndLifeAssuranceCompanyMember
Liberty Life Assurance Company of Boston (A) [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | 4,020 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_LibertyLifeAssuranceCompanyOfBostonMember
Other [Member] |
Commitments And Contingencies [Line Items] |
Statement value of annuities exceeding 1% of statutory surplus | $ 17,824 amsf_StatementValueOfAnnuitiesAsPercentageOfStatutorySurplus / dei_LegalEntityAxis = amsf_OtherLifeInsuranceCompanyMember

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