Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of accounting	The accompanying unaudited consolidated financial statements include the accounts of Wesco Aircraft Holdings, Inc. and its wholly owned subsidiaries (referred to herein as Wesco or the Company) prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) and with the instructions to Form 10-Q and Article 10 of Regulation S-X. The financial statements presented herein have not been audited by an independent registered public accounting firm, but include all material adjustments (consisting of normal recurring adjustments) which are, in the opinion of management, necessary for fair statement of the financial position, results of operations and cash flows for the period. However, these results are not necessarily indicative of results for any other interim period or for the full fiscal year. The preparation of financial statements in conformity with GAAP requires us to make certain estimates and assumptions for the reporting periods covered by the financial statements. These estimates and assumptions affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent liabilities. Actual amounts could differ from these estimates. Our financial statements have been prepared under the assumption that our Company will continue as a going concern. Certain information and footnote disclosures normally included in financial statements in accordance with GAAP have been omitted pursuant to the rules of the Securities and Exchange Commission (the SEC). The accompanying consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K filed with the SEC on November 29, 2017 (the 2017 Form 10-K). Certain reclassifications have been made to the amounts in prior periods to conform to the current period’s presentation.
New Accounting Standards Issued	New Accounting Standards Issued In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which improves the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. ASU 2017-12 expands the eligibility of hedging strategies that qualify for hedge accounting, changes the assessment of hedge effectiveness and modifies the presentation and disclosure of hedging activities. ASU 2017-12 is effective for the Company in 2020 fiscal year including interim reporting periods within that reporting period. Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting, which specifies the modification accounting applicable to any entity that changes the terms or conditions of a share-based payment award. ASU 2017-09 is effective for the Company in fiscal year 2019. Early adoption is permitted. We do not anticipate the adoption of ASU 2017-09 will have a significant impact on our consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which simplifies the current requirements for testing goodwill for impairment by eliminating the second step of the two-step impairment test to measure the amount of an impairment loss. ASU 2017-04 is effective for the Company in fiscal year 2021, including interim reporting periods within that reporting period, and all annual and interim reporting periods thereafter. Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize on the balance sheet a right-of-use asset, representing its right to use the underlying asset for the lease term, and a lease liability for all leases with terms greater than 12 months. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from current GAAP. ASU 2016-02 retains a distinction between finance leases (i.e. capital leases under current GAAP) and operating leases. The classification criteria for distinguishing between finance leases and operating leases will be substantially similar to the classification criteria for distinguishing between capital leases and operating leases under current GAAP. ASU 2016-02 also requires qualitative and quantitative disclosures designed to assess the amount, timing, and uncertainty of cash flows arising from leases. A modified retrospective transition approach shall be used when adopting ASU 2016-02, which includes a number of optional practical expedients that entities may elect to apply. ASU 2016-02 is effective for the Company in fiscal year 2020 and interim periods therein, with early application permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements. As of September 30, 2017, total future minimum payments under our operating leases amounted to $51.4 million. In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, which affects the accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements of financial instruments. ASU 2016-01 is effective for the Company in fiscal year 2019, with early adoption permitted for certain provisions. We are currently evaluating the impact of ASU 2016-01 related to equity investments and the presentation and disclosure requirements of financial instruments on our consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). ASU 2014-09 is amended by ASU 2015-14, ASU 2016-08, ASU 2016-10, ASU 2016-11, ASU 2016-12, ASU 2016-20, ASU 2017-10, ASU 2017-13 and ASU 2017-14, which FASB issued in August 2015, March 2016, April 2016, May 2016, May 2016, December 2016, May 2017, September 2017 and November 2017, respectively (collectively, the amended ASU 2014-09). The amended ASU 2014-09 provides a single comprehensive model for the recognition of revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. It requires an entity to recognize revenue when the entity transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The amended ASU 2014-09 creates a five-step model that requires entities to exercise judgment when considering the terms of contract(s), which includes (1) identifying the contract(s) with the customer, (2) identifying the separate performance obligations in the contract, (3) determining the transaction price, (4) allocating the transaction price to the separate performance obligations, and (5) recognizing revenue as each performance obligation is satisfied. The amended ASU 2014-09 requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including qualitative and quantitative information about contracts with customers, significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The effective date for the amended ASU 2014-09 for the Company is fiscal year 2019, including interim reporting periods within that reporting period. Early adoption is permitted for fiscal year 2018, including interim reporting periods within that reporting period. The amended ASU 2014-09 may have an impact on the timing and amount of revenues and cost of sales in our industry due primarily to changes in whether certain performance obligations are accounted for on a gross or net basis, separating service revenue from the related product revenue, reporting costs currently included in operating expense as costs of services, and capitalizing certain up-front costs related to contracts and amortizing them over the service period. We have completed reviewing our contracts to determine the extent to which these and other issues may impact our results after adoption and are in the process of finalizing our findings from such review before establishing our new accounting policy and control procedures for the amended ASU 2014-09, which we plan to adopt on October 1, 2018 using the modified retrospective method. Adopted Accounting Standards Effective October 1, 2017, we adopted ASU 2016-07, Investments - Equity Method and Joint Ventures (Topic 323), Simplifying the Transition to the Equity Method of Accounting. ASU 2016-07 eliminates the requirement that when an investment subsequently qualifies for use of the equity method as a result of an increase in level of ownership interest or degree of influence, an investor must adjust the investment, results of operations, and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held. ASU 2016-07 requires that the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor’s previously held interest and to adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. In addition, ASU 2016-07 requires that an entity that has an available-for-sale equity security that becomes qualified for the equity method of accounting recognize through earnings the unrealized gain or loss in accumulated other comprehensive income at the date the investment becomes qualified for use of the equity method. The adoption of ASU 2016-07 did not have a material impact on our consolidated financial statements. Effective October 1, 2017, we adopted ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, which requires an entity to measure inventory at the lower of cost and net realizable value, and eliminates current GAAP options for measuring market value. ASU 2015-11 defines realizable value as the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The adoption of ASU 2015-11 did not have a material impact on our consolidated financial statements.

New Accounting Standards Issued

In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which improves the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. ASU 2017-12 expands the eligibility of hedging strategies that qualify for hedge accounting, changes the assessment of hedge effectiveness and modifies the presentation and disclosure of hedging activities. ASU 2017-12 is effective for the Company in 2020 fiscal year including interim reporting periods within that reporting period. Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements.

In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting, which specifies the modification accounting applicable to any entity that changes the terms or conditions of a share-based payment award. ASU 2017-09 is effective for the Company in fiscal year 2019. Early adoption is permitted. We do not anticipate the adoption of ASU 2017-09 will have a significant impact on our consolidated financial statements.

In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which simplifies the current requirements for testing goodwill for impairment by eliminating the second step of the two-step impairment test to measure the amount of an impairment loss. ASU 2017-04 is effective for the Company in fiscal year 2021, including interim reporting periods within that reporting period, and all annual and interim reporting periods thereafter. Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize on the balance sheet a right-of-use asset, representing its right to use the underlying asset for the lease term, and a lease liability for all leases with terms greater than 12 months. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from current GAAP. ASU 2016-02 retains a distinction between finance leases (i.e. capital leases under current GAAP) and operating leases. The classification criteria for distinguishing between finance leases and operating leases will be substantially similar to the classification criteria for distinguishing between capital leases and operating leases under current GAAP. ASU 2016-02 also requires qualitative and quantitative disclosures designed to assess the amount, timing, and uncertainty of cash flows arising from leases. A modified retrospective transition approach shall be used when adopting ASU 2016-02, which includes a number of optional practical expedients that entities may elect to apply. ASU 2016-02 is effective for the Company in fiscal year 2020 and interim periods therein, with early application permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements. As of September 30, 2017, total future minimum payments under our operating leases amounted to $51.4 million.

In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, which affects the accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements of financial instruments. ASU 2016-01 is effective for the Company in fiscal year 2019, with early adoption permitted for certain provisions. We are currently evaluating the impact of ASU 2016-01 related to equity investments and the presentation and disclosure requirements of financial instruments on our consolidated financial statements.

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). ASU 2014-09 is amended by ASU 2015-14, ASU 2016-08, ASU 2016-10, ASU 2016-11, ASU 2016-12, ASU 2016-20, ASU 2017-10, ASU 2017-13 and ASU 2017-14, which FASB issued in August 2015, March 2016, April 2016, May 2016, May 2016, December 2016, May 2017, September 2017 and November 2017, respectively (collectively, the amended ASU 2014-09). The amended ASU 2014-09 provides a single comprehensive model for the recognition of revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. It requires an entity to recognize revenue when the entity transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The amended ASU 2014-09 creates a five-step model that requires entities to exercise judgment when considering the terms of contract(s), which includes (1) identifying the contract(s) with the customer, (2) identifying the separate performance obligations in the contract, (3) determining the transaction price, (4) allocating the transaction price to the separate performance obligations, and (5) recognizing revenue as each performance obligation is satisfied. The amended ASU 2014-09 requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including qualitative and quantitative information about contracts with customers, significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The effective date for the amended ASU 2014-09 for the Company is fiscal year 2019, including interim reporting periods within that reporting period. Early adoption is permitted for fiscal year 2018, including interim reporting periods within that reporting period.

The amended ASU 2014-09 may have an impact on the timing and amount of revenues and cost of sales in our industry due primarily to changes in whether certain performance obligations are accounted for on a gross or net basis, separating service revenue from the related product revenue, reporting costs currently included in operating expense as costs of services, and capitalizing certain up-front costs related to contracts and amortizing them over the service period. We have completed reviewing our contracts to determine the extent to which these and other issues may impact our results after adoption and are in the process of finalizing our findings from such review before establishing our new accounting policy and control procedures for the amended ASU 2014-09, which we plan to adopt on October 1, 2018 using the modified retrospective method.

Adopted Accounting Standards

Effective October 1, 2017, we adopted ASU 2016-07, Investments - Equity Method and Joint Ventures (Topic 323), Simplifying the Transition to the Equity Method of Accounting. ASU 2016-07 eliminates the requirement that when an investment subsequently qualifies for use of the equity method as a result of an increase in level of ownership interest or degree of influence, an investor must adjust the investment, results of operations, and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held. ASU 2016-07 requires that the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor’s previously held interest and to adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. In addition, ASU 2016-07 requires that an entity that has an available-for-sale equity security that becomes qualified for the equity method of accounting recognize through earnings the unrealized gain or loss in accumulated other comprehensive income at the date the investment becomes qualified for use of the equity method. The adoption of ASU 2016-07 did not have a material impact on our consolidated financial statements.

Effective October 1, 2017, we adopted ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, which requires an entity to measure inventory at the lower of cost and net realizable value, and eliminates current GAAP options for measuring market value. ASU 2015-11 defines realizable value as the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The adoption of ASU 2015-11 did not have a material impact on our consolidated financial statements.