Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2025
Related Party Transaction [Line Items]
Basis of Presentation	The Partnership’s condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”). The Partnership’s condensed consolidated financial statements and related financial information have been prepared pursuant to the requirements of Regulation S-X. The Condensed Consolidated Statements of Assets and Liabilities as of December 31, 2024 was derived from the audited annual financial statements. The condensed consolidated financial statements as of June 30, 2025, including these notes, are unaudited. Management believes it has made all necessary adjustments (consisting of only normal recurring items) so that the condensed consolidated financial statements are fairly stated and that estimates made in preparing its condensed consolidated financial statements are reasonable and prudent. The Partnership is considered an investment company under U.S. GAAP and follows the accounting and reporting guidance applicable to investment companies in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 946. The functional currency of the Partnership is U.S. dollars and these condensed consolidated financial statements have been prepared in that currency.
Principles of Consolidation	Principles of Consolidation In accordance with ASC Topic 946, the Partnership generally does not consolidate investments unless the Partnership has a controlling financial interest in an investment company or operating company whose business consists of providing services to the Partnership. A controlling financial interest is defined as (a) the power to direct the activities of the investment company that most significantly impact the entity’s economic performance and (b) the obligation to absorb losses of the entity or the right to receive benefits from the entity that could potentially be significant to the investment company. The General Partner determines whether the Partnership has a controlling financial interest in an investment company at such company’s inception and continuously reconsiders that conclusion. For wholly owned and substantially wholly owned interests in investment companies, the General Partner assesses the nature of the investment structure and considers its interests in and governance rights over the investment company to determine whether the Partnership holds a controlling financial interest. Performance of that analysis requires the exercise of judgment. The Partnership has a controlling financial interest in Stonepeak-Plus Infrastructure Fund Lower Fund VI-A LP (“Lower Fund VI-A”) which wholly owns Stonepeak-Plus Infrastructure Fund Holdco A (CYM) LLC (“Holdco A,” collectively with Lower Fund VI-A, the “Consolidated Entities”), and as a result these entities are consolidated for reporting purposes. All intercompany balances have been eliminated in consolidation. The Partnership does not have a controlling financial interest in and, as a result, does not consolidate the Master Aggregator, nor any other reporting entities within SP+ INFRA (defined as the Fund, together with any Parallel Funds, any Feeder Funds, the Aggregators, the Lower Funds and any other Intermediate Entities, collectively) except for the entities noted above, because (a) the General Partner is not acting solely on behalf of the Partnership as it carries out its duties and (b) the Partnership does not absorb essentially all of the Master Aggregator’s variability. At each reporting date, the General Partner assesses whether the Partnership has a controlling financial interest in the Master Aggregator or any other reporting entities within SP+ INFRA, and any associated consolidation implications.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the Partnership to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates and such differences could be material.
Valuation of Investments at Fair Value	Valuation of Investments at Fair Value The Partnership has indirect exposure to gains and losses on underlying investments because it invests in the Intermediate Entities which, in turn, hold such underlying investments through the Intermediate Entities’ subsidiaries. Valuations of investments held by the Intermediate Entities are disclosed in the notes to the Master Aggregator’s condensed consolidated financial statements included in this report. For information regarding net realized and change in unrealized gains and losses on such investments held indirectly by the Partnership, see the Master Aggregator’s condensed consolidated financial statements attached to this condensed consolidated financial statement included in this report. The Partnership measures its investment in the Intermediate Entities at fair value using the net asset value of the Intermediate Entities. The net asset value of the Intermediate Entities is considered a practical expedient that represents fair value as (a) the investment does not have a readily determinable fair value because the Intermediate Entities’ net asset value is not published or the basis for current transactions, (b) the Intermediate Entities are investment companies and (c) the net asset value of the Intermediate Entities are calculated in a manner in which all of its investments are reported at fair value as of the measurement date. Changes in the fair value of the Partnership’s investment in the Intermediate Entities are presented within net change in unrealized gain (loss) on investments in the Condensed Consolidated Statements of Operations. ASC Topic 820, Fair Value Measurement (“ASC 820”), establishes a hierarchical disclosure framework which prioritizes and ranks the level of market price observability used in measuring investments at fair value. Market price observability is impacted by a number of factors, including the type of investment, the characteristics specific to the investment, and the state of the marketplace. Investments with readily available, actively quoted prices, or for which fair value can be measured from actively quoted prices, generally will have a higher degree of market price observability and a lesser degree of judgment used in measuring fair value. Investments measured and reported at fair value are classified and disclosed in one of the following categories: •Level I – Quoted prices are available in active markets for identical investments as of the reporting date. The type of investments included in Level I are publicly traded securities in an active market. The Master Aggregator does not adjust the quoted price for these investments (to the extent it holds them) even in situations where the Master Aggregator holds a large position and a sale could reasonably impact the quoted price. •Level II – Pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined through the use of models or other valuation methodologies. The types of investments that would generally be included in this category include publicly traded securities with restrictions on disposition, certain convertible securities and certain over-the-counter derivatives where the fair value is based on observable inputs. •Level III – Pricing inputs are unobservable and include situations where there is little, if any, market activity for the investment. Fair value for these investments is determined using valuation methodologies that consider a range of factors, including, but not limited to, the price at which the investment was acquired, the nature of the investment, local market conditions, valuations for comparable companies, current and projected operating performance and financing transactions subsequent to the acquisition of the investment. The inputs into the determination of fair value require significant judgment. Due to the inherent uncertainty of these estimates, these values may differ materially from the values that would have been used had a ready market for these investments existed. Investments that are included in this category generally are privately held debt, equity and certain convertible securities. In certain cases the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, an investment’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The Investment Advisor’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the investment.
Cash	Cash Cash consists of a demand deposit held with a nationally recognized financial institution, which at times may exceed federally insured limits.
Organization Expenses	Organization Expenses Organization expenses include, among other things, the cost of incorporating the Partnership and the cost of legal services and other fees pertaining to the Partnership’s organization. These costs are expensed as incurred. For both the three and six months ended June 30, 2024, the Partnership incurred organization expenses of $571,543.
Offering Costs	Offering Costs Offering costs include registration fees and legal fees regarding the preparation of the initial registration statement and costs in connection with the continuous offering of Units of the Partnership. Offering costs are recognized as a deferred charge and are amortized on a straight-line basis over 12 months beginning on the date of commencement of operations.
Income Recognition	Income Recognition The Partnership recognizes interest income from its affiliated investments when earned pursuant to the terms of the respective investment. The Partnership recognizes dividend income from investments when earned. In the case of proceeds received from investments, the General Partner determines the character of such proceeds and records any interest income, dividend income, realized gain or loss, or return of capital accordingly.
Income Taxes	Income Taxes The Partnership is treated as a partnership for U.S. federal and state income tax purposes, is not directly subject to U.S. federal income taxes, and is generally not directly subject to U.S. state income taxes. The Partnership is subject to the provisions of the Accounting Standard Codification (“ASC”) Topic 740-10 “Accounting for Uncertainty in Income Taxes”. This standard establishes consistent thresholds as it relates to accounting for income taxes. It defines the threshold for recognizing the benefits of tax-return positions in the condensed consolidated financial statements as “more-likely-than-not” to be sustained by the taxing authority and requires measurement of a tax position meeting the more-likely-than-not criterion, based on the largest benefit that is more than 50 percent likely to be realized. The General Partner has analyzed the Partnership’s inventory of tax positions taken with respect to all applicable income tax issues for all open tax years (in each respective jurisdiction), and has concluded that there were no uncertain tax positions that require a provision for income tax in the Partnership’s condensed consolidated financial statements for the three and six months ended June 30, 2025. Interest and penalties assessed by the tax authorities would be recognized as expenses in the period in which they were incurred and are presented as other expenses in the condensed consolidated statement of operations. For the three and six months ended June 30, 2025, there were no income tax expenses and no interest and penalties were incurred. As of June 30, 2025, the tax years that remain subject to examination by the major tax jurisdictions under the statute of limitations are from inception forward. Dividends, as well as certain interest and other income received by the Partnership from sources within the U.S., may be subject to, and reflected gross of, U.S. withholding tax. Interest, dividends and other income realized by the Partnership from non-U.S. sources and capital gains realized on the sale of non-U.S. investments may be subject to withholding and other taxes levied by the jurisdiction in which the income is sourced. Amounts withheld for the payment of U.S. or foreign withholding tax are treated as if such amounts were realized and recognized by the Partnership and distributed to the partners. No provisions have been made in the accompanying condensed consolidated financial statements for federal, state and local income taxes since such liabilities are the responsibility of the individual partners.
Segment Reporting	Segment Reporting The Partnership operates through a single reportable segment. The chief operating decision maker (the “CODM”) is the Chief Executive Officer of the Partnership. The CODM assesses the performance of, allocates resources to and makes operating decisions for the Partnership primarily based on the Partnership’s Net Increase in Net Assets Resulting from Operations. Reportable segment assets are reflected on the accompanying Condensed Consolidated Statements of Assets and Liabilities as Total Assets and reportable segment significant expenses that are regularly provided to the CODM are listed on the accompanying Condensed Consolidated Statements of Operations.
New Accounting Standards	New Accounting Standards In November 2024, the FASB issued Accounting Standards Update No. 2024-03, Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures: Disaggregation of Income Statement Expenses (“ASU 2024-03”). ASU 2024-03 will require more detailed information about the types of expenses in commonly presented income statement captions such as “Cost of sales” and “Selling, general and administrative expenses.” The new guidance is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027 with early adoption permitted. The Partnership is currently evaluating the impact that this change will have on the Partnership's condensed consolidated financial statements.
Stonepeak-Plus Infrastructure Fund Master Aggregator LP
Related Party Transaction [Line Items]
Basis of Presentation	Basis of Presentation The Master Aggregator’s condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”). The Master Aggregator’s condensed consolidated financial statements and related financial information have been prepared pursuant to the requirements of Regulation S-X. The condensed consolidated financial statements as of June 30, 2025, including these notes, are unaudited. Management believes it has made all necessary adjustments (consisting of only normal recurring items) so that the condensed consolidated financial statements are fairly stated and that estimates made in preparing its condensed consolidated financial statements are reasonable and prudent. The Master Aggregator is considered an investment company under U.S. GAAP and follows the accounting and reporting guidance applicable to investment companies in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 946 (“ASC 946”). Accordingly, the Master Aggregator reflects its investments on the Condensed Consolidated Statements of Assets and Liabilities at their fair value with unrealized gains and losses resulting from changes in fair value of its investments reflected in Net change in unrealized gain (loss) on investments on the Condensed Consolidated Statements of Operations. The functional currency of the Master Aggregator is U.S. dollars and these condensed consolidated financial statements have been prepared in that currency.
Principles of Consolidation	Principles of Consolidation In accordance with ASC Topic 946, the Master Aggregator generally does not consolidate investments unless the Master Aggregator has a controlling financial interest in an investment company or operating company whose business consists of providing services to the Master Aggregator. A controlling financial interest is defined as (a) the power to direct the activities of the investment company that most significantly impact the entity’s economic performance and (b) the obligation to absorb losses of the entity or the right to receive benefits from the entity that could potentially be significant to the investment company. The General Partner determines whether the Master Aggregator has a controlling financial interest in an investment company at such company’s inception and continuously reconsiders that conclusion. For wholly owned and substantially wholly owned interests in investment companies, the General Partner assesses the nature of the investment structure and considers its interests in and governance rights over the investment company to determine whether the Master Aggregator holds a controlling financial interest. Performance of that analysis requires the exercise of judgment. The Master Aggregator has a controlling financial interest in Stonepeak Midband (Co-Invest) Holdings LP (“Midband Co-Invest), Stonepeak-Plus Infrastructure Fund Lower Fund III LP (“Lower Fund III”), Stonepeak-Plus Infrastructure Fund Lower Fund IV LP (“Lower Fund IV”), Stonepeak-Plus Infrastructure Fund Standing Intermediate Blocker LP (“Standing Intermediate”), which wholly owns Stonepeak-Plus Infrastructure Fund Lower Fund V LP (“Lower Fund V”), Stonepeak-Plus Infrastructure Fund Aggregator I LP (“Aggregator I”), which wholly owns Stonepeak-Plus Infrastructure Fund Lower Fund I LP (“Lower Fund I”) and Stonepeak-Plus Infrastructure Fund Lower Fund II LP (“Lower Fund II”, collectively with Midband Co-Invest, Lower Fund I, Lower Fund III, Lower Fund IV, and Lower Fund V, the “Consolidated Entities”), and as a result these entities are consolidated for reporting purposes.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the General Partner to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates and such differences could be material.
Valuation of Investments at Fair Value	Fair Value of Investments and Financial Instruments ASC Topic 820, Fair Value Measurement (“ASC 820”), establishes a hierarchical disclosure framework which prioritizes and ranks the level of market price observability used in measuring investments at fair value. Market price observability is impacted by a number of factors, including the type of investment, the characteristics specific to the investment, and the state of the marketplace. Investments with readily available, actively quoted prices, or for which fair value can be measured from actively quoted prices, generally will have a higher degree of market price observability and a lesser degree of judgment used in measuring fair value. Investments measured and reported at fair value are classified and disclosed in one of the following categories: •Level I – Quoted prices are available in active markets for identical investments as of the reporting date. The type of investments included in Level I are publicly traded securities in an active market. The Master Aggregator does not adjust the quoted price for these investments (to the extent it holds them) even in situations where the Master Aggregator holds a large position and a sale could reasonably impact the quoted price. •Level II – Pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined through the use of models or other valuation methodologies. The types of investments that would generally be included in this category include publicly traded securities with restrictions on disposition, certain convertible securities and certain over-the-counter derivatives where the fair value is based on observable inputs. •Level III – Pricing inputs are unobservable and include situations where there is little, if any, market activity for the investment. Fair value for these investments is determined using valuation methodologies that consider a range of factors, including, but not limited to, the price at which the investment was acquired, the nature of the investment, local market conditions, valuations for comparable companies, current and projected operating performance and financing transactions subsequent to the acquisition of the investment. The inputs into the determination of fair value require significant judgment. Due to the inherent uncertainty of these estimates, these values may differ materially from the values that would have been used had a ready market for these investments existed. Investments that are included in this category generally are privately held debt, equity and certain convertible securities. In certain cases the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, an investment’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The Investment Advisor’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the investment. Investments at Fair Value and Investments in Affiliated or Unaffiliated Investee Funds Investments at Fair Value The Master Aggregator values its investments at fair value in accordance with ASC 820. Fair value is the amount that would be received to sell an asset or paid to transfer a liability, in an orderly transaction between market participants at the measurement date. In the absence of observable market prices, the Master Aggregator’s investments are valued using valuation methodologies applied on a consistent basis as described below. Additional information regarding these investments is provided in Note 3. “Investments and Fair Value Measurement.” The General Partner’s determination of fair value is based on the best information available in the circumstances and incorporates the General Partner’s own assumptions, including assumptions that the General Partner believes market participants would use in valuing the investments, and involves a significant degree of judgment, taking into consideration a combination of internal and external factors, including appropriate risk adjustments for non-performance and liquidity. The values estimated by the General Partner may differ significantly from values that would have been used had a readily available market for the investments existed and the differences could be material to the condensed consolidated financial statements. Under the income approach, which is generally the Master Aggregator’s primary valuation approach, fair value is determined by converting future amounts, such as cash flows or earnings, discounted to a single present amount using current market expectations about those future amounts. In determining fair value under this approach, the Master Aggregator makes assumptions over a projection period regarding unobservable inputs such as revenues, operating income, capital expenditures, income taxes, working capital needs and the terminal value and exit multiple of the investee company, among other things. The Master Aggregator discounts those projected cash flows by deriving a discount rate based on a capital structure similar to that of a market participant using observable inputs such as the rate of return available in the market on an investment free of default risk, an equity risk premium to reflect the additional risk of a market portfolio of equity instruments over risk-free instruments, beta as a measure of risk based on share price correlation to the market, and equity and debt-to-capital ratios of companies deemed comparable to the investee company. Under the market approach, which is generally the Master Aggregator’s secondary valuation approach, fair value may be determined by reference to a recent transaction involving the investment or by reference to observable valuation measures for companies or assets that are determined by the Master Aggregator to be comparable, such as multiplying a key performance metric of the investee company, such as earnings before interest and taxes or other performance metric, by a relevant valuation multiple observed in the range of comparable companies or transactions, adjusted by the Master Aggregator for differences between the investment and the referenced comparables. Observable inputs used in the market approach to derive a valuation multiple may include the public prices for securities issued by, and the relevant performance metrics of, companies deemed comparable to the investee company, and/or transaction prices involving significant equity interests in companies deemed comparable to the investee company. Unobservable inputs used in the market approach may include the key performance metric of the investee company, such as earnings before interest, taxes, depreciation and amortization (“EBITDA”). Investments may also be valued at their acquisition price for a period of time after an acquisition as the best measure of fair value in the absence of any conditions or circumstances that would indicate otherwise. In the event of an announced sale of investments with a definitive agreement in place, investments may also be valued using a discount-to-sale approach as the primary method with emphasis given to certain considerations including, but not limited to unitholder approval, regulatory approval, financing, completion of due diligence and break-up fees. Investments in debt securities that are not listed on an exchange, but for which external pricing sources, such as dealer quotes or independent pricing services may be available, are valued by the Master Aggregator after considering, among other factors, such external pricing sources, recent trading activity or market transactions of similar securities adjusted for security specific factors such as relative capital structure priority and interest and yield risks. Publicly traded investments in active markets are reported at the market closing price, less a discount, as appropriate, as determined by the Master Aggregator to reflect restrictions on disposition where such restrictions are an attribute of the investment. Investments in Affiliated or Unaffiliated Investee Funds Investments in SP+ INFRA affiliated investee funds (“Investments in Affiliated Investee Funds”) or unaffiliated investee funds (“Investee Funds”) are generally valued using the reported net asset value (“NAV” or “Net Asset Value”) of the Investee Funds as a practical expedient for fair value. The Master Aggregator may, as a practical expedient, estimate the fair value of an Investee Fund based on NAV if the reported NAV of the Investee Fund is calculated in a manner consistent with the measurement principles applied to investment companies and the Master Aggregator has internal processes to independently evaluate the fair value measurement process utilized by the underlying Investee Fund to calculate the Investee Fund’s NAV, both of which are in accordance with ASC 946. Such internal processes include the evaluation of the Investee Fund’s own process and related internal controls in place to estimate the fair value of its underlying investments that are included in the NAV calculation, performance of ongoing operational due diligence, review of the Investee Fund’s financial statements and ongoing monitoring of other relevant qualitative and quantitative factors. If the General Partner determines, based on its own due diligence and investment monitoring procedures, that NAV does not represent fair value or if the Investee Fund is not an investment company, such as a collateralized loan obligation vehicle, the Master Aggregator will estimate the fair value in good faith and in a manner that it reasonably chooses, in accordance with its valuation policies.
Cash	Cash and Cash Equivalent Cash and cash equivalent represents cash on hand, cash held in banks, money market funds and short-term, and highly liquid investments with original maturities of three months or less. Master Aggregator may have bank balances in excess of federally insured amounts; however, Master Aggregator deposits its cash and cash equivalent with high credit-quality institutions to minimize credit risk.
Organization Expenses	Organization Expenses Organization expenses include, among other things, the cost of incorporating the Master Aggregator and the cost of legal services and other fees pertaining to the Master Aggregator’s organization. These costs are expensed as incurred.
Net Realized and Unrealized Gain (Loss) on Investments	Net Realized and Unrealized Gain (Loss) on Investments The Master Aggregator recognizes net realized gains (losses) on investments when earned at the time of receipt of proceeds. Without regard to unrealized gains or losses previously recognized, realized gains or losses will be measured as the difference between the net proceeds from the sale, repayment or disposal of an asset and the cost basis of the asset. Net change in unrealized gain (loss) on investments is the change in fair value of its underlying investments. Net change in unrealized gains or losses will reflect the change in investment values during the reporting period, including any reversal of previously recorded unrealized gains or losses when gains or losses are realized.
Income Recognition	Income Recognition The Master Aggregator recognizes interest income from private investments when earned pursuant to the terms of the respective investment. The Master Aggregator recognizes dividend income from investments when earned. In the case of proceeds received from investments, the General Partner determines the character of such proceeds and records any interest income, dividend income, realized gain or loss, or return of capital accordingly.
Income Taxes	Income Taxes The Master Aggregator is treated as a partnership for U.S. federal and state income tax purposes, is not directly subject to U.S. federal income taxes, and is generally not directly subject to U.S. state income taxes. It is possible that the Master Aggregator may be considered a publicly traded partnership and not meet the qualifying income exception in certain years. In such a scenario, the Master Aggregator would be treated as a publicly traded partnership taxed as a corporation, rather than a partnership. The investors of the Master Aggregator would be treated as shareholders in a corporation, and the Master Aggregator itself would become taxable as a corporation for U.S. federal, state and/or local income tax purposes. The Master Aggregator would be required to pay income tax at corporate rates on its net taxable income. Additionally, the Master Aggregator owns a controlling interest in several subsidiaries that are treated as corporations for U.S. and non-U.S. tax purposes (“Aggregator Corporations”) which are subject to U.S. federal, state and/or local income taxes. Certain intermediate entities may be formed for use in carrying out the Master Aggregator's activities and these may be subject to income taxes. To the extent investments made by the non-U.S. subsidiaries are engaged in a U.S. trade or business, the subsidiaries will generally be subject to a U.S. federal income tax of 21% of its share of taxable income effectively connected with the conduct of a U.S. trade or business and may be subject to additional branch profits tax of 30% of its share of effectively connected earnings and profits, adjusted as provided by law. The subsidiaries may also be subject to state tax and local taxes. Federal and state income taxes are expected to be withheld at the source of the U.S. trade or business and taxes withheld can be used as a credit against the income tax liability of the subsidiaries. The Master Aggregator consolidates certain wholly-owned subsidiaries that are treated as corporations for U.S. federal income tax purposes. For the three and six months ended June 30, 2025, the Master Aggregator did not have an income tax liability nor benefit.
New Accounting Standards	New Accounting Standards In November 2024, the FASB issued Accounting Standards Update No. 2024-03, Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures: Disaggregation of Income Statement Expenses (“ASU 2024-03”). ASU 2024-03 will require more detailed information about the types of expenses in commonly presented income statement captions such as “Cost of sales” and “Selling, general and administrative expenses.” The new guidance is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027 with early adoption permitted. The Master Aggregator is currently evaluating the impact that this change will have on the Master Aggregator's condensed consolidated financial statements.