Summary of Financial Statement Preparation and Significant Accounting Policies	6 Months Ended
Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Financial Statement Preparation and Significant Accounting Policies	SUMMARY OF FINANCIAL STATEMENT PREPARATION AND SIGNIFICANT ACCOUNTING POLICIES Nature of Operations Air Transport Services Group, Inc. is a holding company whose subsidiaries primarily operate within the airfreight and logistics industry. The Company leases aircraft and provides airline operations, ground services, aircraft modification and maintenance services and other support services. The Company's subsidiaries offer a range of complementary services to delivery companies, freight forwarders, airlines and government customers. The Company's leasing subsidiary, Cargo Aircraft Management, Inc. (“CAM”), leases aircraft to each of the Company's airlines as well as to non-affiliated airlines and other lessees. The airlines, ABX Air, Inc. (“ABX”) and Air Transport International, Inc. (“ATI”), each have the authority, through their separate U.S. Department of Transportation ("DOT") and Federal Aviation Administration ("FAA") certificates, to transport cargo worldwide. The Company's airlines provide a combination of aircraft, crews, maintenance and insurance services for a customer's transportation network through "CMI" and "ACMI" agreements and through charter contracts in which aviation fuel is also included. ATI provides passenger transportation, primarily to the U.S. Military, using "combi" aircraft, which are certified to carry passengers as well as cargo on the main deck. Through its subsidiary Airborne Maintenance and Engineering Services, Inc. ("AMES"), the Company provides aircraft maintenance and modification services. In addition, the Company provides ground equipment maintenance and operates mail and package sorting facilities. Basis of Presentation The accompanying unaudited condensed interim consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America and such principles are applied on a basis consistent with the financial statements reflected in our Annual Report on Form 10-K for the fiscal year ended December 31, 2017 filed with the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to the rules and regulations promulgated by the SEC related to interim financial statements. In the opinion of management, the accompanying financial statements contain all adjustments, including normal recurring adjustments, necessary for the fair presentation of the Company’s results of operations and financial position for the periods presented. Due to seasonal fluctuations, among other factors common to the air cargo industry, the results of operations for the periods presented are not necessarily indicative of the results of operations to be expected for the entire year or any interim period. The preparation of consolidated financial statements requires management to make estimates and assumptions that affect amounts reported in the consolidated financial statements. The accounting estimates reflect the best judgment of management, but actual results could differ materially from those estimates. The accompanying condensed consolidated financial statements include the accounts of Air Transport Services Group, Inc. and its wholly-owned subsidiaries. Investments in affiliates in which the Company has significant influence but does not exercise control are accounted for using the equity method of accounting. Using the equity method, the Company’s share of the nonconsolidated affiliates' income or loss is recognized in the consolidated statement of earnings and cumulative post-acquisition changes in the investment are adjusted against the carrying amount of the investment. Inter-company balances and transactions are eliminated. Accounting Standards Updates Effective January 1, 2018 the Company adopted the Financial Accounting Standards Board's ("FASB") Accounting Standards Update ("ASU") No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” ("Topic 606”) which superseded previous revenue recognition guidance. Topic 606 is a comprehensive new revenue recognition model that requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. The Company's lease revenues within the scope of ASC 840, Leases, are specifically excluded from Topic 606. The Company adopted the standard using a modified retrospective approach, under which financial statements are prepared under the revised guidance for the year of adoption, but not for prior years. Under this method, entities recognize a cumulative catch-up adjustment to the opening balance of retained earnings at the effective date for open contract performance at that time. The Company's adoption efforts included the identification of revenue within the scope of the standard, the evaluation of customer contracts in conjunction with new guidance and an assessment of the qualitative and quantitative impacts of the new standard on its financial statements. The evaluation included the application of each of the five steps identified in the Topic 606 revenue recognition model. The Company determined that under Topic 606, it is an agent for aviation fuel and certain other costs reimbursed by customers under its ACMI and CMI contracts and for certain cargo handling services that it arranges for a customer. Under the new revenue standard, such reimbursed amounts are reported net of the corresponding expenses beginning in 2018. This application of Topic 606 did not have a material impact on the Company's reported earnings in any period. Additionally under Topic 606, the Company is required to record revenue over time, instead of at the time of completion, for certain customer contracts for airframe and modification services that do not have an alternative use and for which the Company has an enforceable right to payment during the service cycle. The Company adopted the provisions of this new standard using the modified retrospective method which requires the Company to record a one time adjustment to retained deficit for the cumulative effect that the standard has on open contracts at the time of adoption. Upon adoption of the new standard the Company accelerated $3.6 million of revenue resulting in an immaterial adjustment to its January 1, 2018 retained deficit for open airframe and modification services contracts. In January 2017, the FASB issued ASU "Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment" (“ASU 2017-04”). This new standard eliminates Step 2 from the goodwill impairment test and requires an entity to perform its goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity recognizes an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. ASU 2017-04 is effective for any annual or interim goodwill impairment tests in the fiscal years beginning after December 15, 2019 and must be applied prospectively. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company adopted this new accounting guidance in January of 2018. The adoption did not have an impact on the Company's financial position, results of operations, or cash flows. In March 2017, the FASB issued ASU "Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost "(ASU 2017-07"). ASU 2017-07 requires an employer to report the service cost component of retiree benefits in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented separately from the service cost component and outside a subtotal of income from operations. The Company adopted ASU 2017-07 on January 1, 2018, retrospectively to all periods presented. As a result, retiree benefit plan interest expense, investment returns, settlements and other non-service cost components of retiree benefit expenses are excluded from the Company's operating income subtotal as reported in the Company's Consolidated Statement of Operations, but remain included in earnings before income taxes. Information about retiree benefit plans' interest expense, investment returns and other components of retiree benefit expenses can be found in Note I. In February 2016, the FASB issued ASU "Leases (Topic 842)" ("ASU 2016-02"), which will require the recognition of right to-use-assets and lease liabilities for leases previously classified as operating leases by lessees. The standard will take effect for annual reporting periods beginning after December 15, 2018, including interim reporting periods. Early application will be permitted for all entities. In addition, the FASB has decided to require a lessee to apply a modified retrospective transition approach for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements (the date of initial application). The modified retrospective approach would not require any transition accounting for leases that expired before the date of initial application. The Company is currently evaluating the impact of the standard on its financial statements and disclosures. In February 2018, the FASB issued ASU “Reclassification of Certain Tax Effects From Accumulated Other Comprehensive Income" ("ASU 2018-02"). ASU 2018-02 amends ASC 220, Income Statement — Reporting Comprehensive Income, to allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from U.S. federal tax legislation known as the Tax Cuts and Jobs Act. In addition, under the ASU 2018-02, a Company will be required to provide certain disclosures regarding stranded tax effects. ASU 2018-02 is effective for years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of the standard on its financial statements and disclosures. In June 2018, the FASB issued ASU “Improvements to Non-employee Share-based Payment Accounting" ("ASU 2018-07"). ASU 2018-07 amends ASC 718, "Compensation - Stock Compensation" ("ASC 718"), to simplify the accounting for share-based payments granted to non-employees for goods and services. ASU 2018-07 supersedes ASC 505-50, "Equity-Based Payments to Non-employees" ("ASC 505-50"). ASU 2018-07 aligns much of the accounting for share-based payments granted to non-employees for goods and services with the accounting for share-based payments granted to employees. ASU 2018-07 is effective for years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. Companies will apply the new guidance to equity-classified non-employee awards for which a measurement date has not been established and liability-classified non-employee awards that have not been settled as of the date of adoption by recognizing a cumulative-effect adjustment to retained earnings as of the beginning of the annual period of adoption. The Company is currently evaluating the impact of the standard on its financial statements and disclosures.

SUMMARY OF FINANCIAL STATEMENT PREPARATION AND SIGNIFICANT ACCOUNTING POLICIES

Nature of Operations

Air Transport Services Group, Inc. is a holding company whose subsidiaries primarily operate within the airfreight and logistics industry. The Company leases aircraft and provides airline operations, ground services, aircraft modification and maintenance services and other support services. The Company's subsidiaries offer a range of complementary services to delivery companies, freight forwarders, airlines and government customers.

The Company's leasing subsidiary, Cargo Aircraft Management, Inc. (“CAM”), leases aircraft to each of the Company's airlines as well as to non-affiliated airlines and other lessees. The airlines, ABX Air, Inc. (“ABX”) and Air Transport International, Inc. (“ATI”), each have the authority, through their separate U.S. Department of Transportation ("DOT") and Federal Aviation Administration ("FAA") certificates, to transport cargo worldwide. The Company's airlines provide a combination of aircraft, crews, maintenance and insurance services for a customer's transportation network through "CMI" and "ACMI" agreements and through charter contracts in which aviation fuel is also included. ATI provides passenger transportation, primarily to the U.S. Military, using "combi" aircraft, which are certified to carry passengers as well as cargo on the main deck. Through its subsidiary Airborne Maintenance and Engineering Services, Inc. ("AMES"), the Company provides aircraft maintenance and modification services. In addition, the Company provides ground equipment maintenance and operates mail and package sorting facilities.

Basis of Presentation

The accompanying unaudited condensed interim consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America and such principles are applied on a basis consistent with the financial statements reflected in our Annual Report on Form 10-K for the fiscal year ended December 31, 2017 filed with the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to the rules and regulations promulgated by the SEC related to interim financial statements. In the opinion of management, the accompanying financial statements contain all adjustments, including normal recurring adjustments, necessary for the fair presentation of the Company’s results of operations and financial position for the periods presented. Due to seasonal fluctuations, among other factors common to the air cargo industry, the results of operations for the periods presented are not necessarily indicative of the results of operations to be expected for the entire year or any interim period. The preparation of consolidated financial statements requires management to make estimates and assumptions that affect amounts reported in the consolidated financial statements. The accounting estimates reflect the best judgment of management, but actual results could differ materially from those estimates.

The accompanying condensed consolidated financial statements include the accounts of Air Transport Services Group, Inc. and its wholly-owned subsidiaries. Investments in affiliates in which the Company has significant influence but does not exercise control are accounted for using the equity method of accounting. Using the equity method, the Company’s share of the nonconsolidated affiliates' income or loss is recognized in the consolidated statement of earnings and cumulative post-acquisition changes in the investment are adjusted against the carrying amount of the investment. Inter-company balances and transactions are eliminated.

Accounting Standards Updates

Effective January 1, 2018 the Company adopted the Financial Accounting Standards Board's ("FASB") Accounting Standards Update ("ASU") No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” ("Topic 606”) which superseded previous revenue recognition guidance. Topic 606 is a comprehensive new revenue recognition model that requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. The Company's lease revenues within the scope of ASC 840, Leases, are specifically excluded from Topic 606.

The Company adopted the standard using a modified retrospective approach, under which financial statements are prepared under the revised guidance for the year of adoption, but not for prior years. Under this method, entities recognize a cumulative catch-up adjustment to the opening balance of retained earnings at the effective date for open contract performance at that time. The Company's adoption efforts included the identification of revenue within the scope of the standard, the evaluation of customer contracts in conjunction with new guidance and an assessment of the qualitative and quantitative impacts of the new standard on its financial statements. The evaluation included the application of each of the five steps identified in the Topic 606 revenue recognition model.

The Company determined that under Topic 606, it is an agent for aviation fuel and certain other costs reimbursed by customers under its ACMI and CMI contracts and for certain cargo handling services that it arranges for a customer. Under the new revenue standard, such reimbursed amounts are reported net of the corresponding expenses beginning in 2018. This application of Topic 606 did not have a material impact on the Company's reported earnings in any period. Additionally under Topic 606, the Company is required to record revenue over time, instead of at the time of completion, for certain customer contracts for airframe and modification services that do not have an alternative use and for which the Company has an enforceable right to payment during the service cycle. The Company adopted the provisions of this new standard using the modified retrospective method which requires the Company to record a one time adjustment to retained deficit for the cumulative effect that the standard has on open contracts at the time of adoption. Upon adoption of the new standard the Company accelerated $3.6 million of revenue resulting in an immaterial adjustment to its January 1, 2018 retained deficit for open airframe and modification services contracts.

In January 2017, the FASB issued ASU "Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment" (“ASU 2017-04”). This new standard eliminates Step 2 from the goodwill impairment test and requires an entity to perform its goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity recognizes an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. ASU 2017-04 is effective for any annual or interim goodwill impairment tests in the fiscal years beginning after December 15, 2019 and must be applied prospectively. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company adopted this new accounting guidance in January of 2018. The adoption did not have an impact on the Company's financial position, results of operations, or cash flows.

In March 2017, the FASB issued ASU "Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost "(ASU 2017-07"). ASU 2017-07 requires an employer to report the service cost component of retiree benefits in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented separately from the service cost component and outside a subtotal of income from operations. The Company adopted ASU 2017-07 on January 1, 2018, retrospectively to all periods presented. As a result, retiree benefit plan interest expense, investment returns, settlements and other non-service cost components of retiree benefit expenses are excluded from the Company's operating income subtotal as reported in the Company's Consolidated Statement of Operations, but remain included in earnings before income taxes. Information about retiree benefit plans' interest expense, investment returns and other components of retiree benefit expenses can be found in Note I.

In February 2016, the FASB issued ASU "Leases (Topic 842)" ("ASU 2016-02"), which will require the recognition of right to-use-assets and lease liabilities for leases previously classified as operating leases by lessees. The standard will take effect for annual reporting periods beginning after December 15, 2018, including interim reporting periods. Early application will be permitted for all entities. In addition, the FASB has decided to require a lessee to apply a modified retrospective transition approach for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements (the date of initial application). The modified retrospective approach would not require any transition accounting for leases that expired before the date of initial application. The Company is currently evaluating the impact of the standard on its financial statements and disclosures.

In February 2018, the FASB issued ASU “Reclassification of Certain Tax Effects From Accumulated Other Comprehensive Income" ("ASU 2018-02"). ASU 2018-02 amends ASC 220, Income Statement — Reporting Comprehensive Income, to allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from U.S. federal tax legislation known as the Tax Cuts and Jobs Act. In addition, under the ASU 2018-02, a Company will be required to provide certain disclosures regarding stranded tax effects. ASU 2018-02 is effective for years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of the standard on its financial statements and disclosures.

In June 2018, the FASB issued ASU “Improvements to Non-employee Share-based Payment Accounting" ("ASU 2018-07"). ASU 2018-07 amends ASC 718, "Compensation - Stock Compensation" ("ASC 718"), to simplify the accounting for share-based payments granted to non-employees for goods and services. ASU 2018-07 supersedes ASC 505-50, "Equity-Based Payments to Non-employees" ("ASC 505-50"). ASU 2018-07 aligns much of the accounting for share-based payments granted to non-employees for goods and services with the accounting for share-based payments granted to employees. ASU 2018-07 is effective for years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. Companies will apply the new guidance to equity-classified non-employee awards for which a measurement date has not been established and liability-classified non-employee awards that have not been settled as of the date of adoption by recognizing a cumulative-effect adjustment to retained earnings as of the beginning of the annual period of adoption. The Company is currently evaluating the impact of the standard on its financial statements and disclosures.