Document and Entity Information [Abstract] Document and Entity Information [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Statement Of Financial Position [Abstract] Statement of Financial Position [Abstract] Statement, Scenario [Axis] Statement, Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Series Fifteen [Member] Series Fifteen [Member] Series Sixteen [Member] Series Sixteen [Member] Series Seventeen [Member] Series Seventeen [Member] Series Eighteen [Member] Series Eighteen [Member] Series Nineteen [Member] Series Nineteen [Member] Assets [Abstract] ASSETS Cash and Cash Equivalents, At Carrying Value Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value, Total Cash and cash equivalents, beginning Cash and cash equivalents, ending Other Assets Other assets Other assets Assets Assets, Total Assets Liabilities [Abstract] LIABILITIES Accounts Payable and Accrued Liabilities Accounts payable & accrued expenses Accounts Payable and Accrued Liabilities, Total Due To Affiliate Accounts payable affiliates (Note C) Capital Contributions Payable Capital contributions payable Capital contributions payable Carrying value of the capital contribution payable to operating partnerships. Under the terms of the Partnership's investment in each Operating Partnership, the Partnership is required to make capital contributions to the Operating Partnerships. These contributions are payable in installments over several years upon each Operating Partnership achieving specified levels of construction and/or operations. Liabilities Liabilities Liabilities Partners Capital [Abstract] PARTNERS' CAPITAL (DEFICIT) Limited Partners Capital Account Units of limited partnership interest Limited Partners' Capital Account, Total General Partners Capital Account General Partner General Partner Partners Capital Partners' capital (deficit) Partners' capital (deficit) Partners' capital (deficit) Partners' capital (deficit) Partners' Capital Liabilities and Stockholders Equity Liabilities and Stockholders' Equity, Total Liabilities and Stockholders' Equity Balance Sheet Parenthetical [Abstract] Balance Sheet Parenthetical [Abstract] Partners Capital Account, Distribution Per Unit Of Limited Partner Interest Beneficial assignee certificate, par value (in dollars per share) Limited Partners Capital Account, Units Authorized Units of limited partnership interest, authorized Limited Partners Capital Account, Units Issued Units of limited partnership interest, issued Limited Partners Capital Account, Units Outstanding Units of limited partnership interest, outstanding Income Statement [Abstract] Income Statement [Abstract] Revenues [Abstract] Revenues Income Interest Income, Operating Interest income Other Real Estate Revenue Other income Other income Revenues Revenues Revenues Income (Loss) From Equity Method Investments Gain/(Loss) on Disposition Share of Income from Operating Partnerships(Note D) Share of Income from Operating Partnerships (Note D) Share of Income from Operating Partnerships Gain/(Loss) on Disposition Operating Expenses [Abstract] Expenses Professional Fees Professional fees Fund Management Fee Fund management fee, net (Note C) Annual fund management fee charged on all apartment complexes owned by the Operating Partnerships net of reporting fees. General and Administrative Expense General and administrative expenses General and administrative expenses Total Expenses Operating Expenses Operating expenses Total Amount of expenses incurred during the year by the entity. Net Income (Loss) Attributable To Parent Net Income (Loss) NET INCOME (LOSS) NET INCOME (LOSS) Net income (loss) Net Income (Loss) Allocated To Limited Partners Net income (loss) allocated to limited assignees Net income (loss) allocated to limited assignees Net income (loss) allocated to limited assignees Net Income (Loss) Allocated To General Partners Net income (loss) allocated to general partner Net income (loss) allocated to general partner Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic Net income (loss) per BAC Net income (loss) per BAC Statement Of Partners Capital [Abstract] Statement of Partners' Capital [Abstract] Related Party Transactions, By Related Party [Axis] Related Party Transactions, by Related Party [Axis] Assignees [Member] General Partner [Member] Statement Of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Net Cash Provided By (Used In) Operating Activities [Abstract] Cash flows from operating activities: Adjustments To Reconcile Net Income (Loss) To Cash Provided By (Used In) Operating Activities [Abstract] Adjustments to reconcile net income (loss) to net cash (used in) provided by operating activities Increase (Decrease) In Operating Capital [Abstract] Changes in assets and liabilities Increase (Decrease) In Other Accounts Payable and Accrued Liabilities (Decrease) Increase in accounts payable and accrued expenses Increase (Decrease) In Other Operating Assets (Increase) Decrease in other assets Decrease (Increase) in other assets Increase (Decrease) In Due To Affiliates, Current (Decrease) Increase in accounts payable affiliates (Decrease) Increase in accounts payable affiliates Net Cash Provided By (Used In) Operating Activities Net cash (used in) provided by operating activities Net cash (used in) provided by operating activities Net Cash Provided By (Used In) Investing Activities [Abstract] Cash flows from investing activities: Proceeds From Sale Of Equity Method Investments Fund Proceeds from Disposition Proceeds from the disposition of Operating Partnerships Proceeds from the disposition ofOperating Partnerships Net Cash Provided By (Used In) Investing Activities Net cash provided by investing activities Net cash provided by investing activities Net Cash Provided By (Used In) Financing Activities [Abstract] Cash flows from financing activities: Payments Of Distributions To Affiliates Distributions Net Cash Provided By (Used In) Financing Activities Net cash used in financing activities Cash and Cash Equivalents, Period Increase (Decrease) INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS Organization, Consolidation and Presentation Of Financial Statements [Abstract] Organization [Abstract] Organization, Consolidation and Presentation Of Financial Statements Disclosure [Text Block] Organization, Consolidation and Presentation Of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Accounting and Financial Reporting Policies [Abstract] Significant Accounting Policies [Text Block] Significant Accounting Policies [Text Block] Related Party Transactions [Abstract] Related Party Transactions [Abstract] Related Party Transactions Disclosure [Text Block] Related Party Transactions Disclosure [Text Block] Equity Method Investments and Joint Ventures [Abstract] Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract] Equity Method Investments Disclosure [Text Block] Equity Method Investments Disclosure [Text Block] Taxable Loss [Abstract] Taxable Loss [Abstract] Taxable Loss [Text Block] Taxable Loss [Text Block] This item represents the expected change in the Partnership's taxable loss for financial reporting purposes. This is primarily due to accounting differences in depreciation incurred by the Operating Partnerships and also differences between the equity method of accounting and IRS accounting methods. Income Tax Disclosure [Abstract] Income Taxes [Abstract] Income Tax Relating To Partnership Disclosure [Text Block] Income Tax Relating To Partnership Disclosure [Text Block] Description containing the income tax disclosure relating to Partnership that has elected to be treated as a pass-through entity for income tax purposes and, as such, is not subject to income taxes. Schedule Of Gross Management Fee [Table Text Block] Schedule Of Gross Management Fee [Table Text Block] Tabular disclosure for gross management fee. Schedule Of Management Fees Paid [Table Text Block] Schedule Of Management Fees Paid [Table Text Block] Tabular disclosure for management fees paid. Schedule Of Number Of Operating Partnerships [Table Text Block] Schedule Of Number Of Operating Partnerships [Table Text Block] Tabular disclosure for number of operating partnerships. Schedule Of Contributions Payable [Table Text Block] Schedule Of Contributions Payable [Table Text Block] Tabular disclosure for contributions payable. Schedule Of Dispositions By Series [Table Text Block] Schedule Of Dispositions By Series [Table Text Block] Tabular disclosure for dispositions by series. Schedule Of Condensed Income Statement [Table Text Block] Schedule Of Condensed Income Statement [Table Text Block] Limited Partners Capital Account Additional Units Registered For Sale Limited Partners Capital Account Additional Units Registered For Sale The additional number of limited partners units registered for sale. Limited Partners Capital Accounts Units Issued Value Limited Partners Capital Accounts Units Issued Value The total amount of limited partnership units issued. Percentage Of Annual Management Fee Percentage Of Annual Management Fee The percentage of annual management fee. Gross Management Fee Accrued management fees Gross amount of management fee during the period. Management Fees Paid Fund management fees paid Amount of management fees paid during the period. Number Of Operating Partnerships Number Of Operating Partnerships Number of operating partnerships. Operating Partnership Interest Transferred Operating Partnership Interest Transferred The number of operating partnership interest transferred. Sale Of Underlying Operating Partnership Sale of Underlying Operating Partnership The number of sale of underlying operating partnership. Operating Partnerships Rental Income Rental The amount of rental income by an operating partnerships of the entity. Operating Partnerships Interest and Other Income Interest and other The amount of interest and other income by an operating partnerships of the entity. Operating Partnerships Revenues Operating Partnerships Revenues Operating Partnerships Revenues The amount of revenues by an operating partnerships of the entity. Expenses [Abstract] Expenses Operating Partnerships Interest Expenses Interest The amount of interest expenses by an operating partnerships of the entity. Operating Partnerships Depreciation and Amortization Depreciation and amortization The amount of depreciation and amortization by an operating partnerships of the entity. Operating Partnerships Operating Expenses Operating expenses The amount of operating expenses by an operating partnerships of the entity. Operating Partnerships Total Expenses Operating Partnerships Total Expenses Operating Partnerships Total Expenses The amount of total expenses by an operating partnerships of the entity. Operating Partnerships Net Loss NET LOSS NET LOSS The amount of net loss by an operating partnerships of the entity. Operating Partnerships Net Loss Allocated To Parent Net loss allocation to Boston Capital Tax Credit Fund III L.P.* The amount of net loss allocated to parent by an operating partnerships of the entity. Operating Partnerships Net Loss Allocated To Other Partners Net loss allocated to other Partners The amount of net loss allocated to other partners by an operating partnerships of the entity. Write Off Of Capital Contribution Payable Write Off Of Capital Contribution Payable Amount of write off of capital contribution payable. Income Loss Not Recognized Under Equity Method Accounting Income Loss Not Recognized Under Equity Method Accounting Amount of income loss not recognized under equity method accounting. Related Party [Domain] Related Party [Domain] Fund Receivable Amount of fund receivable as of the reporting date.