Basis of Presentation (Notes)	9 Months Ended
Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
New Accounting Pronouncements, Policy [Policy Text Block]	NOTE 2. Basis of Presentation We prepared the accompanying unaudited consolidated financial statements in accordance with US Generally Accepted Accounting Principles ("GAAP") for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, our unaudited consolidated financial statements do not include all of the information and footnotes required for complete financial statements. We have included all of the normal recurring adjustments that we deemed necessary for a fair presentation. Operating results for the nine months ended September 30, 2017, are not necessarily indicative of the results we may achieve for the entire year ending December 31, 2017. In particular, ASC's fleet is inactive for a significant portion of the first quarter of each year due to winter conditions on the Great Lakes. In addition, asset remarketing income does not occur evenly throughout the year. For more information, refer to the consolidated financial statements and footnotes in our Annual Report on Form 10-K for the year ended December 31, 2016. New Accounting Pronouncements Adopted Equity Method and Joint Ventures In March 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-07, Investments - Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting, which eliminates the requirement to retrospectively apply equity method accounting when an entity increases ownership or influence in a previously held investment. The new guidance was effective for us in the first quarter of 2017. Application of the new guidance did not impact our financial statements or related disclosures. Stock Compensation In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which simplifies and clarifies certain aspects of share-based payments accounting and presentation. The update requires recognition of excess tax benefits and tax deficiencies, which arise due to differences between the measure of compensation expense and the amount deductible for tax purposes, to be recorded directly through earnings as a component of income tax expense. Previously, these differences were generally recorded in additional paid-in capital and thus had no impact on net income. The change in treatment of excess tax benefits and tax deficiencies also impacts the computation of diluted earnings per share, and the cash flows associated with those items are classified as operating activities on the consolidated statements of cash flows. The guidance also clarifies that all cash payments made to taxing authorities on the employees' behalf for withheld shares should be classified as financing activities on the consolidated statements of cash flows. Additionally, the guidance permits entities to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated as of the initial valuation date, as allowed under the previous guidance, or recognized when they occur. We changed our accounting policy to recognize forfeitures when they occur as part of this adoption. These amendments became effective in the first quarter of 2017, and we adopted this guidance as of January 1, 2017. Adoption of this new standard did not have a material impact on our financial statements or related disclosures. Statement of Cash Flows In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which clarifies the classification and presentation of changes in restricted cash on the statement of cash flows. We elected to early adopt the new guidance as of January 1, 2017, using the retrospective method. Application of the new guidance requires presentation of restricted cash together with cash and cash equivalents on the consolidated statements of cash flows and eliminates the disclosure of the related changes in restricted cash within investing activities. New Accounting Pronouncements Not Yet Adopted Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes most current revenue recognition guidance, including industry-specific guidance. Subsequently, the FASB has issued updates which provide additional implementation guidance. The new guidance requires companies to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration it expects to be entitled to in exchange for those goods or services. The FASB delayed the effective date of this guidance to the first quarter of 2018, with early adoption permitted as of the original effective date of the first quarter of 2017. We plan to adopt this guidance as of January 1, 2018, using the modified retrospective approach. Our primary source of revenue is lease revenue, which will continue to be within the scope of existing lease accounting guidance upon adoption of Topic 606. We have substantially completed our review of all other revenue sources in scope for the new standard and have concluded the new guidance will not have a material impact on our financial statements. Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which supersedes most current lease guidance. The new guidance requires companies to recognize most leases on the balance sheet and modifies accounting, presentation, and disclosure for both lessors and lessees. The new guidance is effective for us in the first quarter of 2019, with early adoption permitted. We plan to adopt this guidance on January 1, 2019, using a modified retrospective transition method, and we expect to utilize the package of three optional practical expedients as provided in the standard. We continue to assess the effect the new guidance will have on our consolidated financial statements and related disclosures. Financial Instruments In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities, which modifies the accounting and reporting requirements for certain equity securities and financial liabilities. The new guidance is effective for us beginning in the first quarter of 2018, with certain provisions eligible for early adoption. We do not expect the new guidance to have a significant impact on our financial statements or related disclosures. Credit Losses In June 2016, the FASB issued ASU 2016-13, Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which modifies how entities will measure credit losses. The new guidance is effective for us in the first quarter of 2020, with early adoption permitted. We are evaluating the effect the new guidance will have on our financial statements and related disclosures. Statement of Cash Flows In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, which clarifies the classification of certain cash receipts and payments in the statement of cash flows. The new guidance is effective for us in the first quarter of 2018, with early adoption permitted. We do not expect the new guidance to have a significant impact on our financial statements or related disclosures. Income Taxes In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory, which modifies how an entity will recognize the income tax consequences of an intra-entity transfer of an asset when the transfer occurs. The new guidance is effective for us in the first quarter of 2018, with early adoption permitted. We plan to adopt this guidance on January 1, 2018, applying the retrospective method. We do not expect the new guidance to have a material impact on our financial statements and related disclosures. Compensation In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, which modifies how an entity must present service costs and other components of net benefit cost. The new guidance is effective for us in the first quarter of 2018, with early adoption permitted. We plan to adopt this guidance on January 1, 2018, applying the retrospective method. We do not expect the new guidance to have a significant impact on our financial statements and related disclosures. Derivatives and Hedging In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which expands and refines hedge accounting for both financial and non-financial risk components, aligns the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and includes certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. The update to the standard is effective for us beginning in the first quarter of 2019, with early adoption permitted in any interim period. We do not expect the new guidance to have a significant impact on our financial statements or related disclosures.

NOTE 2. Basis of Presentation

We prepared the accompanying unaudited consolidated financial statements in accordance with US Generally Accepted Accounting Principles ("GAAP") for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, our unaudited consolidated financial statements do not include all of the information and footnotes required for complete financial statements. We have included all of the normal recurring adjustments that we deemed necessary for a fair presentation.

Operating results for the nine months ended September 30, 2017, are not necessarily indicative of the results we may achieve for the entire year ending December 31, 2017. In particular, ASC's fleet is inactive for a significant portion of the first quarter of each year due to winter conditions on the Great Lakes. In addition, asset remarketing income does not occur evenly throughout the year. For more information, refer to the consolidated financial statements and footnotes in our Annual Report on Form 10-K for the year ended December 31, 2016.

New Accounting Pronouncements Adopted

Equity Method and Joint Ventures

In March 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-07, Investments - Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting, which eliminates the requirement to retrospectively apply equity method accounting when an entity increases ownership or influence in a previously held investment. The new guidance was effective for us in the first quarter of 2017. Application of the new guidance did not impact our financial statements or related disclosures.

Stock Compensation

In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which simplifies and clarifies certain aspects of share-based payments accounting and presentation. The update requires recognition of excess tax benefits and tax deficiencies, which arise due to differences between the measure of compensation expense and the amount deductible for tax purposes, to be recorded directly through earnings as a component of income tax expense. Previously, these differences were generally recorded in additional paid-in capital and thus had no impact on net income. The change in treatment of excess tax benefits and tax deficiencies also impacts the computation of diluted earnings per share, and the cash flows associated with those items are classified as operating activities on the consolidated statements of cash flows. The guidance also clarifies that all cash payments made to taxing authorities on the employees' behalf for withheld shares should be classified as financing activities on the consolidated statements of cash flows. Additionally, the guidance permits entities to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated as of the initial valuation date, as allowed under the previous guidance, or recognized when they occur. We changed our accounting policy to recognize forfeitures when they occur as part of this adoption. These amendments became effective in the first quarter of 2017, and we adopted this guidance as of January 1, 2017. Adoption of this new standard did not have a material impact on our financial statements or related disclosures.

Statement of Cash Flows

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which clarifies the classification and presentation of changes in restricted cash on the statement of cash flows. We elected to early adopt the new guidance as of January 1, 2017, using the retrospective method. Application of the new guidance requires presentation of restricted cash together with cash and cash equivalents on the consolidated statements of cash flows and eliminates the disclosure of the related changes in restricted cash within investing activities.

New Accounting Pronouncements Not Yet Adopted

Revenue from Contracts with Customers

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes most current revenue recognition guidance, including industry-specific guidance. Subsequently, the FASB has issued updates which provide additional implementation guidance. The new guidance requires companies to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration it expects to be entitled to in exchange for those goods or services. The FASB delayed the effective date of this guidance to the first quarter of 2018, with early adoption permitted as of the original effective date of the first quarter of 2017. We plan to adopt this guidance as of January 1, 2018, using the modified retrospective approach. Our primary source of revenue is lease revenue, which will continue to be within the scope of existing lease accounting guidance upon adoption of Topic 606. We have substantially completed our review of all other revenue sources in scope for the new standard and have concluded the new guidance will not have a material impact on our financial statements.

Leases

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which supersedes most current lease guidance. The new guidance requires companies to recognize most leases on the balance sheet and modifies accounting, presentation, and disclosure for both lessors and lessees. The new guidance is effective for us in the first quarter of 2019, with early adoption permitted. We plan to adopt this guidance on January 1, 2019, using a modified retrospective transition method, and we expect to utilize the package of three optional practical expedients as provided in the standard. We continue to assess the effect the new guidance will have on our consolidated financial statements and related disclosures.

Financial Instruments

In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities, which modifies the accounting and reporting requirements for certain equity securities and financial liabilities. The new guidance is effective for us beginning in the first quarter of 2018, with certain provisions eligible for early adoption. We do not expect the new guidance to have a significant impact on our financial statements or related disclosures.

Credit Losses

In June 2016, the FASB issued ASU 2016-13, Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which modifies how entities will measure credit losses. The new guidance is effective for us in the first quarter of 2020, with early adoption permitted. We are evaluating the effect the new guidance will have on our financial statements and related disclosures.

Statement of Cash Flows

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, which clarifies the classification of certain cash receipts and payments in the statement of cash flows. The new guidance is effective for us in the first quarter of 2018, with early adoption permitted. We do not expect the new guidance to have a significant impact on our financial statements or related disclosures.

Income Taxes

In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory, which modifies how an entity will recognize the income tax consequences of an intra-entity transfer of an asset when the transfer occurs. The new guidance is effective for us in the first quarter of 2018, with early adoption permitted. We plan to adopt this guidance on January 1, 2018, applying the retrospective method. We do not expect the new guidance to have a material impact on our financial statements and related disclosures.

Compensation

In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, which modifies how an entity must present service costs and other components of net benefit cost. The new guidance is effective for us in the first quarter of 2018, with early adoption permitted. We plan to adopt this guidance on January 1, 2018, applying the retrospective method. We do not expect the new guidance to have a significant impact on our financial statements and related disclosures.

Derivatives and Hedging

In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which expands and refines hedge accounting for both financial and non-financial risk components, aligns the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and includes certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. The update to the standard is effective for us beginning in the first quarter of 2019, with early adoption permitted in any interim period. We do not expect the new guidance to have a significant impact on our financial statements or related disclosures.