Name:	bftcviii_GeneralPartnerCumulativeEarningsSharingPercentage
Namespace Prefix:	bftcviii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of cumulative earnings allocated to the limited partners based on the sharing of income or losses between general and limited partners as specified in the partnership agreement.

No definition available.

Name:	bftcviii_LimitedPartnersCumulativeEarningsSharingPercentage
Namespace Prefix:	bftcviii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The average number of shares or units issued and outstanding that are used in calculating basic and diluted EPS.

No definition available.

Name:	bftcviii_LimitedPartnerUnits
Namespace Prefix:	bftcviii_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Represents the per unit price of limited partner units.

No definition available.

Name:	bftcviii_LimitedPartnerUnitsPricePerUnit
Namespace Prefix:	bftcviii_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Represents the amount designated as reserves, under the partnership agreement.

No definition available.

Name:	bftcviii_LocalLimitedPartnershipsReserves
Namespace Prefix:	bftcviii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The percentage of cumulative amount of earnings allocated to limited partners as a result of net proceeds from sale or refinancing.

No definition available.

Name:	bftcviii_NetProceedsFromSaleRefinancingGeneralPartnerSharingPercentage
Namespace Prefix:	bftcviii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of cumulative amount of earnings allocated to general partners as a result of net proceeds from sale or refinancing.

No definition available.

Name:	bftcviii_NetProceedsFromSaleRefinancingLimitedPartnersSharingPercentage
Namespace Prefix:	bftcviii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of gross proceeds designated as reserves.

No definition available.

Name:	bftcviii_PercentageOfGrossProceedsDesignatedAsReserves
Namespace Prefix:	bftcviii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The cash inflow from the issuance of limited partners units during the period.

No definition available.

Name:	bftcviii_ProceedsFromIssuanceOfLimitedPartnersUnits
Namespace Prefix:	bftcviii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The number of units or percentage investment held by one or more members or limited partners of the LLC or LP.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The number of limited partner units authorized to be issued.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 5

-Subparagraph (SAB TOPIC 4.F)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187171-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section F

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 87-21

-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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Practice Bulletin (PB)

-Number 14

-Paragraph 10

-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.

Name:	us-gaap_LimitedPartnersCapitalAccountUnitsAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The number of limited partner units issued.