SUMMARY OF SIGNIFCANT ACCOUNTING POLICIES (Policies)	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial results of Altus Midstream are included in Altus Midstream Company’s consolidated financial statements due to Altus Midstream Company’s 100 percent ownership interest in Altus Midstream GP, and Altus Midstream GP’s control of Altus Midstream. Altus Midstream Company has no independent operations or material assets other than its partnership interests in Altus Midstream, which constitutes all of its business. Altus Midstream Company’s only material net assets separate from Altus Midstream relate to deferred taxes and the current and deferred income tax expense (benefit) associated with its investment in Altus Midstream. The deferred tax asset balance was $67.3 million and $67.6 million as of March 31, 2019 and December 31, 2018, respectively. Additionally, Altus Midstream Company’s balance sheet reflects the presentation of noncontrolling interest ownership attributable to the limited partner interests in Altus Midstream held by Apache. Refer to Note 11 — Income Taxes and Note 12 — Equity for further information.
Variable Interest Entity	Variable Interest Entity Altus Midstream is a variable interest entity (VIE) because the partners in Altus Midstream with equity at risk lack the power, through voting or similar rights, to direct the activities that most significantly impact Altus Midstream’s economic performance. A reporting entity that concludes it has a variable interest in a VIE must evaluate whether it has a controlling financial interest in the VIE, such that it is the VIE’s primary beneficiary and should consolidate. Altus Midstream Company is the primary beneficiary of, and therefore should consolidate Altus Midstream because (i) Altus Midstream Company has the power to direct the activities of Altus Midstream that most significantly affect its economic performance and (ii) Altus Midstream Company has the right to receive benefits or the obligation to absorb losses that could be potentially significant to Altus Midstream.
Financial Statement Presentation	Financial Statement Presentation While Altus Midstream Company (formerly KAAC) was the surviving legal entity, the Business Combination was accounted for as a reverse recapitalization. As such, Altus Midstream Company was treated as the acquired company for financial reporting purposes. As a result of the Altus Midstream Entities being the accounting acquirer, the historical operations of the Altus Midstream Entities are deemed to be those of the Company. Thus, the financial statements included in this report reflect (i) the historical operating results of the Altus Midstream Entities prior to the Business Combination; (ii) the net assets of the Altus Midstream Entities at their historical cost; (iii) the consolidated results of the Company and the Altus Midstream Entities following the closing of the Business Combination; and (iv) the Company’s equity structure for all periods presented. No step-up in basis of the contributed assets and no intangible assets or goodwill was recorded in the Business Combination.
Use of Estimates	Use of EstimatesPreparation of financial statements in conformity with GAAP and disclosure of contingent assets and liabilities requires management to make estimates and assumptions that affect reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates on historical experience and various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about carrying values of assets and liabilities that are not readily apparent from other sources. The Company evaluates its estimates and assumptions on a regular basis. Actual results may differ from these estimates and assumptions used in preparation of its financial statements and changes in these estimates are recorded when known.
Fair Value Measurements	Fair Value Measurements The Company’s redeemable noncontrolling interest, as presented in the consolidated financial statements, is reported at fair value on a recurring basis on the Company’s consolidated balance sheet. Accounting Standards Codification (ASC) 820-10-35 - Fair Value Measurement (ASC 820), provides a hierarchy that prioritizes and defines the types of inputs used to measure fair value. The fair value hierarchy gives the highest priority to Level 1 inputs, which consist of unadjusted quoted prices for identical instruments in active markets. Level 2 inputs consist of quoted prices for similar instruments. Level 3 valuations are derived from inputs that are significant and unobservable; hence, these valuations have the lowest priority. The valuation techniques that may be used to measure fair value include a market approach, an income approach and a cost approach. A market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. The Company utilizes the market approach in recurring fair value measurement of the redeemable noncontrolling interest. The Company has classified this fair value assessment as Level 1 in the fair value hierarchy.
Accounts Receivable From/Payable To Apache	Accounts Receivable From/Payable To ApacheThe accounts receivable from or payable to Apache represent the net result of Altus Midstream’s monthly revenue, capital and operating expenditures, and other miscellaneous transactions to be settled with Apache as provided under the COMA. Generally, cash in this amount will be transferred to Apache in the month after the Company’s transactions are processed and the net results of operations are determined. However, from time to time, the Company may estimate and transfer the cash settlement amount in the month the transactions are processed, in order to minimize related-party working capital balances.
Leases	Leases On January 1, 2019, the Company adopted ASU 2016-02, “Leases (Topic 842),” which requires lessees to recognize separate right-of-use (ROU) assets and lease liabilities for most leases classified as operating leases under previous GAAP. Prior to adoption, the Financial Accounting Standards Board (FASB) issued transition guidance permitting an entity the option to not evaluate under ASU 2016-02 those existing or expired land easements that were not previously accounted for as leases, as well as an option to apply the provisions of the new standard at its adoption date instead of the earliest comparative period presented in the consolidated financial statements. The Company elected both transitional practical expedients. Under these transition options, comparative reporting was not required, and the provisions of the standard were applied prospectively to leases in effect at the date of adoption. As allowed under the standard, the Company also applied practical expedients to carry forward its historical assessments of whether existing agreements contain a lease, classification of existing lease agreements, and treatment of initial direct lease costs. The Company also elected to exclude short-term leases (those with terms of 12 months or less) from the balance sheet presentation and accounts for non-lease and lease components as a single lease component for all asset classes. Short-term lease expense was not material for the first quarter of 2019. The Company determines if an arrangement is an operating or finance lease at the inception of each contract. If the contract is classified as an operating lease, Altus records a ROU asset and corresponding liability reflecting the total remaining present value of fixed lease payments over the expected term of the lease agreement. The expected term of the lease may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. In the normal course of business, the Company enters into various lease agreements for real estate and equipment related to its midstream activities which are typically classified as operating leases under the provisions of the standard. ROU assets are reflected within “Deferred charges and other” on the Company’s consolidated balance sheet, and the associated operating lease liabilities are reflected within “Other current liabilities” and “Other noncurrent liabilities,” as applicable. Operating lease expense associated with the ROU assets is recognized on a straight-line basis over the lease term. Lease expense is reflected on the statement of consolidated operations commensurate with the leased activities and nature of the services performed. Fixed operating lease expense was $0.2 million for the three months ended March 31, 2019. In addition, the Company periodically enters into finance leases that are similar to those leases classified as capital leases under previous GAAP. The Company currently has one short-term finance lease, which is included in “Property, Plant and Equipment” on the consolidated balance sheet, and the associated finance lease liability is reflected within “Current debt.”
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, “Financial Instruments - Credit Losses.” The standard changes the impairment model for most financial assets and certain other instruments, including trade and other receivables, held-to-maturity debt securities and loans, and requires entities to use a new forward-looking expected loss model that will result in the earlier recognition of allowance for losses. This update is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Entities will apply the standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company is evaluating the new guidance and does not believe this standard will have a material impact on the consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, “Disclosure Framework: Changes to the Disclosure Requirements for Fair Value Measurement,” which changes the disclosure requirements for fair value measurements by removing, adding, and modifying certain disclosures. ASU 2018-13 is effective for financial statements issued for annual periods beginning after December 15, 2019, and interim periods within those annual periods. Early adoption is permitted. The Company is currently evaluating the impact of adoption of this ASU on its related disclosures.
Revenue recognition	The Company currently generates all its revenues by providing the above services, pursuant to separate midstream service agreements entered into with Apache. These midstream service agreements have no minimum volume commitments or firm transportation commitments, instead they are underpinned by acreage dedications covering Alpine High. Pursuant to these agreements, Altus Midstream is obligated to perform services on all volumes produced from the dedicated acreage, so long as Apache has the right to market such gas. In exchange for the above services and in accordance with the terms of the midstream service agreements, the Company charges a fixed fee on a per unit basis. These performance obligations are satisfied over time as Apache simultaneously receives and consumes the benefits of the services performed. Service revenues are recognized when the right to invoice has been met, since the amount that the Company has the right to invoice (based upon the fixed fee and throughput volumes) corresponds directly with the value received by Apache. Pursuant to the terms of the Contribution Agreement, all accounts receivable from Apache (including revenue receivable) on or prior to September 30, 2018, are for the account of Apache. No cash settlement of such balances was contemplated prior to September 30, 2018 and as such, revenue receivables generated prior to this date were treated as a reduction to additional paid-in capital within equity. Following the Business Combination, service revenue invoices are provided to Apache on a monthly basis, pursuant to the terms of the COMA. Amounts owing to Apache under the terms of the COMA are reduced by the amounts of these invoices. Net cash settlement is performed on a monthly basis. The net amount of receivable from Apache as of March 31, 2019 relating to revenue earned and invoiced was $10.6 million. Additionally, the Company recognized services revenue earned but not yet invoiced to Apache of $11.5 million as of March 31, 2019. Costs to obtain a contract with expected amortization periods of greater than one year will be recorded as an asset and will be recognized in accordance with ASC 340, “Other Assets and Deferred Costs.” Currently, Altus Midstream does not have contract assets related to incremental costs to obtain a contract. In addition, the Company does not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less or contracts for which variable consideration is allocated entirely to a wholly unsatisfied performance obligation.

SUMMARY OF SIGNIFCANT ACCOUNTING POLICIES (Policies)

3 Months Ended

Mar. 31, 2019

The consolidated financial results of Altus Midstream are included in Altus Midstream Company’s consolidated financial statements due to Altus Midstream Company’s 100 percent ownership interest in Altus Midstream GP, and Altus Midstream GP’s control of Altus Midstream.

Altus Midstream Company has no independent operations or material assets other than its partnership interests in Altus Midstream, which constitutes all of its business. Altus Midstream Company’s only material net assets separate from Altus Midstream relate to deferred taxes and the current and deferred income tax expense (benefit) associated with its investment in Altus Midstream. The deferred tax asset balance was $67.3 million and $67.6 million as of March 31, 2019 and December 31, 2018, respectively. Additionally, Altus Midstream Company’s balance sheet reflects the presentation of noncontrolling interest ownership attributable to the limited partner interests in Altus Midstream held by Apache. Refer to Note 11 — Income Taxes and Note 12 — Equity for further information.

Variable Interest Entity

Altus Midstream is a variable interest entity (VIE) because the partners in Altus Midstream with equity at risk lack the power, through voting or similar rights, to direct the activities that most significantly impact Altus Midstream’s economic performance.

A reporting entity that concludes it has a variable interest in a VIE must evaluate whether it has a controlling financial interest in the VIE, such that it is the VIE’s primary beneficiary and should consolidate. Altus Midstream Company is the primary beneficiary of, and therefore should consolidate Altus Midstream because (i) Altus Midstream Company has the power to direct the activities of Altus Midstream that most significantly affect its economic performance and (ii) Altus Midstream Company has the right to receive benefits or the obligation to absorb losses that could be potentially significant to Altus Midstream.

Financial Statement Presentation

While Altus Midstream Company (formerly KAAC) was the surviving legal entity, the Business Combination was accounted for as a reverse recapitalization. As such, Altus Midstream Company was treated as the acquired company for financial reporting purposes.

As a result of the Altus Midstream Entities being the accounting acquirer, the historical operations of the Altus Midstream Entities are deemed to be those of the Company. Thus, the financial statements included in this report reflect (i) the historical operating results of the Altus Midstream Entities prior to the Business Combination; (ii) the net assets of the Altus Midstream Entities at their historical cost; (iii) the consolidated results of the Company and the Altus Midstream Entities following the closing of the Business Combination; and (iv) the Company’s equity structure for all periods presented. No step-up in basis of the contributed assets and no intangible assets or goodwill was recorded in the Business Combination.

Use of Estimates

Use of EstimatesPreparation of financial statements in conformity with GAAP and disclosure of contingent assets and liabilities requires management to make estimates and assumptions that affect reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates on historical experience and various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about carrying values of assets and liabilities that are not readily apparent from other sources. The Company evaluates its estimates and assumptions on a regular basis. Actual results may differ from these estimates and assumptions used in preparation of its financial statements and changes in these estimates are recorded when known.

Fair Value Measurements

The Company’s redeemable noncontrolling interest, as presented in the consolidated financial statements, is reported at fair value on a recurring basis on the Company’s consolidated balance sheet. Accounting Standards Codification (ASC) 820-10-35 - Fair Value Measurement (ASC 820), provides a hierarchy that prioritizes and defines the types of inputs used to measure fair value. The fair value hierarchy gives the highest priority to Level 1 inputs, which consist of unadjusted quoted prices for identical

instruments in active markets. Level 2 inputs consist of quoted prices for similar instruments. Level 3 valuations are derived from inputs that are significant and unobservable; hence, these valuations have the lowest priority.

The valuation techniques that may be used to measure fair value include a market approach, an income approach and a cost approach. A market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. The Company utilizes the market approach in recurring fair value measurement of the redeemable noncontrolling interest. The Company has classified this fair value assessment as Level 1 in the fair value hierarchy.

Accounts Receivable From/Payable To Apache

Accounts Receivable From/Payable To ApacheThe accounts receivable from or payable to Apache represent the net result of Altus Midstream’s monthly revenue, capital and operating expenditures, and other miscellaneous transactions to be settled with Apache as provided under the COMA. Generally, cash in this amount will be transferred to Apache in the month after the Company’s transactions are processed and the net results of operations are determined. However, from time to time, the Company may estimate and transfer the cash settlement amount in the month the transactions are processed, in order to minimize related-party working capital balances.

Leases

On January 1, 2019, the Company adopted ASU 2016-02, “Leases (Topic 842),” which requires lessees to recognize separate right-of-use (ROU) assets and lease liabilities for most leases classified as operating leases under previous GAAP. Prior to adoption, the Financial Accounting Standards Board (FASB) issued transition guidance permitting an entity the option to not evaluate under ASU 2016-02 those existing or expired land easements that were not previously accounted for as leases, as well as an option to apply the provisions of the new standard at its adoption date instead of the earliest comparative period presented in the consolidated financial statements. The Company elected both transitional practical expedients. Under these transition options, comparative reporting was not required, and the provisions of the standard were applied prospectively to leases in effect at the date of adoption.

As allowed under the standard, the Company also applied practical expedients to carry forward its historical assessments of whether existing agreements contain a lease, classification of existing lease agreements, and treatment of initial direct lease costs. The Company also elected to exclude short-term leases (those with terms of 12 months or less) from the balance sheet presentation and accounts for non-lease and lease components as a single lease component for all asset classes. Short-term lease expense was not material for the first quarter of 2019.

The Company determines if an arrangement is an operating or finance lease at the inception of each contract. If the contract is classified as an operating lease, Altus records a ROU asset and corresponding liability reflecting the total remaining present value of fixed lease payments over the expected term of the lease agreement. The expected term of the lease may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. In the normal course of business, the Company enters into various lease agreements for real estate and equipment related to its midstream activities which are typically classified as operating leases under the provisions of the standard. ROU assets are reflected within “Deferred charges and other” on the Company’s consolidated balance sheet, and the associated operating lease liabilities are reflected within “Other current liabilities” and “Other noncurrent liabilities,” as applicable.

Operating lease expense associated with the ROU assets is recognized on a straight-line basis over the lease term. Lease expense is reflected on the statement of consolidated operations commensurate with the leased activities and nature of the services performed. Fixed operating lease expense was $0.2 million for the three months ended March 31, 2019.

In addition, the Company periodically enters into finance leases that are similar to those leases classified as capital leases under previous GAAP. The Company currently has one short-term finance lease, which is included in “Property, Plant and Equipment” on the consolidated balance sheet, and the associated finance lease liability is reflected within “Current debt.”

Recently Issued Accounting Standards Not Yet Adopted

In June 2016, the FASB issued ASU 2016-13, “Financial Instruments - Credit Losses.” The standard changes the impairment model for most financial assets and certain other instruments, including trade and other receivables, held-to-maturity debt securities and loans, and requires entities to use a new forward-looking expected loss model that will result in the earlier recognition of allowance for losses. This update is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Entities will apply the standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company is evaluating the new guidance and does not believe this standard will have a material impact on the consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13, “Disclosure Framework: Changes to the Disclosure Requirements for Fair Value Measurement,” which changes the disclosure requirements for fair value measurements by removing, adding, and modifying certain disclosures. ASU 2018-13 is effective for financial statements issued for annual periods beginning after December 15, 2019, and interim periods within those annual periods. Early adoption is permitted. The Company is currently evaluating the impact of adoption of this ASU on its related disclosures.

Revenue recognition

The Company currently generates all its revenues by providing the above services, pursuant to separate midstream service agreements entered into with Apache. These midstream service agreements have no minimum volume commitments or firm transportation commitments, instead they are underpinned by acreage dedications covering Alpine High. Pursuant to these agreements, Altus Midstream is obligated to perform services on all volumes produced from the dedicated acreage, so long as Apache has the right to market such gas. In exchange for the above services and in accordance with the terms of the midstream service agreements, the Company charges a fixed fee on a per unit basis.

These performance obligations are satisfied over time as Apache simultaneously receives and consumes the benefits of the services performed. Service revenues are recognized when the right to invoice has been met, since the amount that the Company has the right to invoice (based upon the fixed fee and throughput volumes) corresponds directly with the value received by Apache.

Pursuant to the terms of the Contribution Agreement, all accounts receivable from Apache (including revenue receivable) on or prior to September 30, 2018, are for the account of Apache. No cash settlement of such balances was contemplated prior to September 30, 2018 and as such, revenue receivables generated prior to this date were treated as a reduction to additional paid-in capital within equity. Following the Business Combination, service revenue invoices are provided to Apache on a monthly basis, pursuant to the terms of the COMA. Amounts owing to Apache under the terms of the COMA are reduced by the amounts of these invoices. Net cash settlement is performed on a monthly basis. The net amount of receivable from Apache as of March 31, 2019 relating to revenue earned and invoiced was $10.6 million. Additionally, the Company recognized services revenue earned but not yet invoiced to Apache of $11.5 million as of March 31, 2019.

Costs to obtain a contract with expected amortization periods of greater than one year will be recorded as an asset and will be recognized in accordance with ASC 340, “Other Assets and Deferred Costs.” Currently, Altus Midstream does not have contract assets related to incremental costs to obtain a contract. In addition, the Company does not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less or contracts for which variable consideration is allocated entirely to a wholly unsatisfied performance obligation.