2.4.0.8022 - Disclosure - Investments in Local Limited Partnerships (Details Textual)truefalsefalse1false USDfalsefalse$Context_FYE_31-Mar-2013http://www.sec.gov/CIK0000911568duration2012-04-01T00:00:002013-03-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$Context_FYE_31-Mar-2012http://www.sec.gov/CIK0000911568duration2011-04-01T00:00:002012-03-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1false 4bftcviii_CumulativeUnrecognizedEquityLossesInLocalLimitedPartnershipsbftcviii_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse945515945515USD$falsetruefalse2truefalsefalse32029283202928USD$falsetruefalsexbrli:monetaryItemTypemonetaryRepresents the value of cumulative unrecognized equity losses in local limited partnerships as of balance sheet date.No definition available.false2Cumulative Unrecognized Equity Losses In Local Limited Partnerships2false 4bftcviii_UnrecognizedEquityLossesOnLocalLimitedPartnershipInvestmentsbftcviii_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse50005000USD$falsefalsefalse2truefalsefalse8000080000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents unrecognized loss from local limited liability partnership investments due to cumulative distributions and losses exceeds the total investments.No definition available.false2Estimated Equity in Income (Losses) of Local Limited Partnership Investments3false 4us-gaap_ProceedsFromLimitedPartnershipInvestmentsus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse20150002015000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCash inflow received as distributions, returns of capital, or sale proceeds from partnership interests held for investment purposes.No definition available.false2Proceeds from Limited Partnership Investments4false 4us-gaap_InvestmentOwnedAtFairValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse19896811989681USD$falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryValue of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 14 -Paragraph Column E -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12C -Paragraph Column C -Article 12 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 13 -Paragraph Column C -Article 12 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12.Column C.3,4) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611133-123010 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-12C.Column C.7) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611225-123010 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14.Column E.2,3) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611322-123010 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 5 -Subparagraph (SX 210.12-13.Column C.6) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611282-123010 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph Column C -Article 12 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph 3, 4 -Article 12 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 14 -Paragraph 2, 3 -Article 12 Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 13 -Paragraph 6 -Article 12 Reference 12: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12C -Paragraph 7 -Article 12 false2Investment Owned, at Fair Value5false 4us-gaap_GainOnSaleOfInvestmentsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalselabel1truefalsefalse2531925319USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.No definition available.false2Gain on Sale of Investments6false 4bftcviii_UnrecognizedEquityLossesCumulativeEquityInLossesAndDistributionsInExcessOfTotalInvestmentbftcviii_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalse1truefalsefalse3864738647USD$falsefalsefalse2truefalsefalse9111291112USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the unrecognized equity in losses relating to certain Local Limited Partnerships in which cumulative equity in losses and distributions exceeded its total investment in the Local Limited Partnerships.No definition available.false2Unrecognized Equity Losses Cumulative Equity In Losses And Distributions In Excess Of Total Investment7false 4bftcviii_UnrecognizedEquityLossesInLocalLimitedPartnershipbftcviii_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse15279471527947USD$falsetruefalse2truefalsefalse446090446090USD$falsetruefalsexbrli:monetaryItemTypemonetaryRepresents the value of unrecognized equity losses in local limited partnerships during the period.No definition available.false2Previously unrecognized equity in losses of Local Limited Partnership8false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3false truefalseContext_FYE_31-Mar-2013_LegalEntityAxis_OtherLocalLimitedPartnershipsMemberhttp://www.sec.gov/CIK0000911568duration2012-04-01T00:00:002013-03-31T00:00:00falsefalseOther Local Limited Partnerships [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldibftcviii_OtherLocalLimitedPartnershipsMemberdei_LegalEntityAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0nanafalse0Other Local Limited Partnerships [Member]9false 4us-gaap_SubsidiaryOfLimitedLiabilityCompanyOrLimitedPartnershipOwnershipInterestus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse0.990.99falsefalsefalse2falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe number of units or percentage investment held in the subsidiary by the limited liability company or limited partnership.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 22 -Article 12 false0Subsidiary of Limited Liability Company or Limited Partnership, Ownership Interest10false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse4false truefalseContext_FYE_31-Mar-2013_LegalEntityAxis_HemlockRidgeLimitedPartnershipMemberhttp://www.sec.gov/CIK0000911568duration2012-04-01T00:00:002013-03-31T00:00:00falsefalseHemlock Ridge Limited Partnership [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldibftcviii_HemlockRidgeLimitedPartnershipMemberdei_LegalEntityAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0nanafalse0Hemlock Ridge Limited Partnership [Member]11false 4us-gaap_SubsidiaryOfLimitedLiabilityCompanyOrLimitedPartnershipOwnershipInterestus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse0.770.77falsefalsefalse2falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe number of units or percentage investment held in the subsidiary by the limited liability company or limited partnership.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 22 -Article 12 false0Subsidiary of Limited Liability Company or Limited Partnership, Ownership InterestfalseInvestments in Local Limited Partnerships (Details Textual) (USD $)NoRoundingUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.bostonfinancial.com/role/InvestmentsInLocalLimitedPartnershipsDetailsTextual211