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CONDENSED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (DEFICIT) (USD $)
Total
Limited Partners [Member]
General Partner [Member]
Series Twenty [Member]
Series Twenty [Member]
Limited Partners [Member]
Series Twenty [Member]
General Partner [Member]
Series Twenty One [Member]
Series Twenty One [Member]
Limited Partners [Member]
Series Twenty One [Member]
General Partner [Member]
Series Twenty Two [Member]
Series Twenty Two [Member]
Limited Partners [Member]
Series Twenty Two [Member]
General Partner [Member]
Series Twenty Three [Member]
Series Twenty Three [Member]
Limited Partners [Member]
Series Twenty Three [Member]
General Partner [Member]
Series Twenty Four [Member]
Series Twenty Four [Member]
Limited Partners [Member]
Series Twenty Four [Member]
General Partner [Member]
Series Twenty Five [Member]
Series Twenty Five [Member]
Limited Partners [Member]
Series Twenty Five [Member]
General Partner [Member]
Series Twenty Six [Member]
Series Twenty Six [Member]
Limited Partners [Member]
Series Twenty Six [Member]
General Partner [Member]
Series Twenty Seven [Member]
Series Twenty Seven [Member]
Limited Partners [Member]
Series Twenty Seven [Member]
General Partner [Member]
Series Twenty Eight [Member]
Series Twenty Eight [Member]
Limited Partners [Member]
Series Twenty Eight [Member]
General Partner [Member]
Series Twenty Nine [Member]
Series Twenty Nine [Member]
Limited Partners [Member]
Series Twenty Nine [Member]
General Partner [Member]
Series Thirty [Member]
Series Thirty [Member]
Limited Partners [Member]
Series Thirty [Member]
General Partner [Member]
Series Thirty One [Member]
Series Thirty One [Member]
Limited Partners [Member]
Series Thirty One [Member]
General Partner [Member]
Series Thirty Two [Member]
Series Thirty Two [Member]
Limited Partners [Member]
Series Thirty Two [Member]
General Partner [Member]
Series Thirty Three [Member]
Series Thirty Three [Member]
Limited Partners [Member]
Series Thirty Three [Member]
General Partner [Member]
Series Thirty Four [Member]
Series Thirty Four [Member]
Limited Partners [Member]
Series Thirty Four [Member]
General Partner [Member]
Series Thirty Five [Member]
Series Thirty Five [Member]
Limited Partners [Member]
Series Thirty Five [Member]
General Partner [Member]
Series Thirty Six [Member]
Series Thirty Six [Member]
Limited Partners [Member]
Series Thirty Six [Member]
General Partner [Member]
Series Thirty Seven [Member]
Series Thirty Seven [Member]
Limited Partners [Member]
Series Thirty Seven [Member]
General Partner [Member]
Series Thirty Eight [Member]
Series Thirty Eight [Member]
Limited Partners [Member]
Series Thirty Eight [Member]
General Partner [Member]
Series Thirty Nine [Member]
Series Thirty Nine [Member]
Limited Partners [Member]
Series Thirty Nine [Member]
General Partner [Member]
Series Forty [Member]
Series Forty [Member]
Limited Partners [Member]
Series Forty [Member]
General Partner [Member]
Series Forty One [Member]
Series Forty One [Member]
Limited Partners [Member]
Series Forty One [Member]
General Partner [Member]
Series Forty Two [Member]
Series Forty Two [Member]
Limited Partners [Member]
Series Forty Two [Member]
General Partner [Member]
Series Forty Three [Member]
Series Forty Three [Member]
Limited Partners [Member]
Series Forty Three [Member]
General Partner [Member]
Series Forty Four [Member]
Series Forty Four [Member]
Limited Partners [Member]
Series Forty Four [Member]
General Partner [Member]
Series Forty Five [Member]
Series Forty Five [Member]
Limited Partners [Member]
Series Forty Five [Member]
General Partner [Member]
Series Forty Six [Member]
Series Forty Six [Member]
Limited Partners [Member]
Series Forty Six [Member]
General Partner [Member]
Partners capital (deficit) at Mar. 31, 2014 $ (32,337,277)us-gaap_PartnersCapital $ (24,847,683)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
$ (7,489,594)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
$ (1,283,326)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
$ (962,241)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
$ (321,085)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
$ (1,268,340)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
$ (1,093,706)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
$ (174,634)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
$ (2,802,821)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
$ (2,555,709)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
$ (247,112)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
$ (2,431,408)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
$ (2,122,247)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
$ (309,161)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
$ 887,715us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
$ 1,064,135us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
$ (176,420)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
$ 2,551,311us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
$ 2,783,242us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
$ (231,931)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
$ 2,504,077us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
$ 2,819,289us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
$ (315,212)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
$ 1,001,929us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
$ 1,198,357us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
$ (196,428)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
$ (235,971)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
$ 110,137us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
$ (346,108)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
$ (3,367,939)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyNineMember
$ (2,995,613)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyNineMember
$ (372,326)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyNineMember
$ (1,563,761)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyMember
$ (1,321,067)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyMember
$ (242,694)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyMember
$ (2,403,752)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyOneMember
$ (2,000,456)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyOneMember
$ (403,296)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyOneMember
$ (2,778,502)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyTwoMember
$ (2,344,354)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyTwoMember
$ (434,148)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyTwoMember
$ (1,819,023)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyThreeMember
$ (1,575,053)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyThreeMember
$ (243,970)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyThreeMember
$ (3,604,793)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFourMember
$ (3,268,355)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFourMember
$ (336,438)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFourMember
$ (1,978,984)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFiveMember
$ (1,677,169)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFiveMember
$ (301,815)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFiveMember
$ (791,172)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySixMember
$ (604,597)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySixMember
$ (186,575)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySixMember
$ (1,980,418)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySevenMember
$ (1,745,050)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySevenMember
$ (235,368)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySevenMember
$ (1,479,945)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyEightMember
$ (1,246,861)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyEightMember
$ (233,084)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyEightMember
$ (1,403,805)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyNineMember
$ (1,193,325)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyNineMember
$ (210,480)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyNineMember
$ (2,731,739)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyMember
$ (2,479,478)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyMember
$ (252,261)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyMember
$ (2,886,394)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyOneMember
$ (2,608,361)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyOneMember
$ (278,033)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyOneMember
$ (1,804,351)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyTwoMember
$ (1,545,369)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyTwoMember
$ (258,982)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyTwoMember
$ (1,880,062)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyThreeMember
$ (1,539,740)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyThreeMember
$ (340,322)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyThreeMember
$ (1,604,389)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFourMember
$ (1,350,897)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFourMember
$ (253,492)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFourMember
$ 650,896us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFiveMember
$ 998,049us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFiveMember
$ (347,153)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFiveMember
$ 2,167,690us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember
$ 2,408,756us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember
$ (241,066)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember
Net income (loss) 4,728,401us-gaap_NetIncomeLoss 4,681,118us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
47,283us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
102,587us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
101,561us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
1,026us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
(28,379)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
(28,095)us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
(284)us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
118,544us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
117,359us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
1,185us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
398,363us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
394,379us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
3,984us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
(77,720)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
(76,943)us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
(777)us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
1,270,127us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
1,257,426us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
12,701us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
487,597us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
482,721us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
4,876us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
77,839us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
77,061us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
778us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
5,540,419us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
5,485,015us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
55,404us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
75,296us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyNineMember
74,543us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyNineMember
753us-gaap_NetIncomeLoss
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
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/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember
1,773,546us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= bctciv_LimitedPartnersMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember
(247,482)us-gaap_PartnersCapital
/ us-gaap_PartnerTypeOfPartnersCapitalAccountAxis
= us-gaap_GeneralPartnerMember
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember
Partners capital (deficit) at Sep. 30, 2014                                                                                                                                                                        
Net income (loss) 359,209us-gaap_NetIncomeLoss     166,586us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
    (19,047)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
    165,747us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
    457,714us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
    (20,790)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
    65,109us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
    47,722us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
    (34,857)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
    57,375us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
    242,056us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyNineMember
    26,091us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyMember
    129,572us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyOneMember
    (23,086)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyTwoMember
    (36,095)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyThreeMember
    (58,828)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFourMember
    (52,539)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFiveMember
    (29,586)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySixMember
    (39,265)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySevenMember
    (19,914)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyEightMember
    (9,188)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyNineMember
    (55,926)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyMember
    (63,872)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyOneMember
    (61,450)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyTwoMember
    (103,604)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyThreeMember
    (69,173)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFourMember
    (117,997)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFiveMember
    (183,546)us-gaap_NetIncomeLoss
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember
   
Partners capital (deficit) at Dec. 31, 2014 $ (27,608,876)us-gaap_PartnersCapital     $ (1,180,739)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyMember
    $ (1,296,719)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyOneMember
    $ (2,684,277)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyTwoMember
    $ (2,033,045)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyThreeMember
    $ 809,995us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFourMember
    $ 3,821,438us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyFiveMember
    $ 2,991,674us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySixMember
    $ 1,079,768us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentySevenMember
    $ 5,304,448us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyEightMember
    $ (3,292,643)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesTwentyNineMember
    $ (1,634,438)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyMember
    $ (2,428,571)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyOneMember
    $ (2,940,954)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyTwoMember
    $ (1,921,421)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyThreeMember
    $ (3,801,800)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFourMember
    $ (2,144,698)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyFiveMember
    $ (872,855)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySixMember
    $ (2,115,913)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtySevenMember
    $ (1,567,667)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyEightMember
    $ (1,493,939)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesThirtyNineMember
    $ (2,906,958)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyMember
    $ (3,078,701)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyOneMember
    $ (1,942,611)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyTwoMember
    $ (2,136,138)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyThreeMember
    $ (1,810,696)us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFourMember
    $ 142,520us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortyFiveMember
    $ 1,526,064us-gaap_PartnersCapital
/ bctciv_TaxCreditSeriesAxis
= bctciv_SeriesFortySixMember