Significant Subsidiaries (Details Textual)	9 Months Ended
Dec. 31, 2012
Equity Method Investment, Ownership Percentage Criteria	The following Local Limited Partnerships invested in by the Fund represent more than 20% of the Fund's total assets or equity as of December 31, 2012 or 2011 or net income (loss) for the three months then ended.

Description about the percentage criteria of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

No definition available.

Name:	bftcpa_EquityMethodInvestmentOwnershipPercentageCriteria
Namespace Prefix:	bftcpa_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration