Basis of Presentation Basis of Presentation (Notes)	3 Months Ended
Mar. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	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 three months ended March 31, 2016, are not necessarily indicative of the results we may achieve for the entire year ending December 31, 2016. 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, 2015. Accounting Changes Change in Accounting Estimate At the end of 2015, we changed the approach used to measure service and interest costs for pension and other postretirement benefits. In prior years, the Company measured service and interest costs utilizing a single weighted-average discount rate derived from the yield curve used to measure the plan obligations. For 2016, we measured service and interest costs by applying the specific spot rates along that yield curve to the plans’ liability cash flows. The Company believes this approach provides a more precise measurement of service and interest costs by aligning the timing of the plans’ liability cash flows to the corresponding spot rates on the yield curve. This change does not affect the measurement of our plan obligations. The Company has accounted for this change as a change in accounting estimate and, accordingly, has accounted for it on a prospective basis. The Company's adoption of the full yield curve approach will reduce 2016 service and interest cost by approximately $4.5 million ($2.8 million after-tax) as compared to the previous method. New Accounting Pronouncements Adopted Consolidation In February 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2015-02, Consolidation (Topic 810) Amendments to the Consolidation Analysis, which amends the analysis required to determine whether to consolidate certain types of legal entities such as limited partnerships, limited liability corporations, and certain securitization structures. The new guidance was effective for us beginning in the first quarter of 2016. Application of the new guidance did not impact our financial statements or related disclosures. Business Combinations In September 2015, the FASB issued ASU 2015-16, Business Combinations (Topic 805), Simplifying the Accounting for Measurement-Period Adjustments, which requires the acquirer in a business combination to recognize measurement-period adjustments in the period in which it determines the amount of the adjustment. The new guidance was effective for us in the first quarter of 2016. Application of the new guidance did not impact our financial statements or related disclosures. 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 can adopt the new guidance using either the retrospective method or the cumulative effect transition method. We are evaluating the effect that the new guidance will have on our consolidated financial statements and related disclosures and when we will elect to adopt this standard. 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, using a modified retrospective transition method. We are evaluating the effect that the new guidance will have on our consolidated financial statements and related disclosures and when we will elect to adopt this standard. Financial Instruments In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall: 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. Equity Method and Joint Ventures In March 2016, the FASB issued 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 is effective for us in the first quarter of 2017 with early adoption permitted. We do not expect the new guidance to 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 payment accounting and presentation. The new guidance is effective for us in the first quarter of 2017 with early adoption permitted. We are evaluating the effect that the new guidance will have on our financial statements and related disclosures.

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 three months ended March 31, 2016, are not necessarily indicative of the results we may achieve for the entire year ending December 31, 2016. 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, 2015.

Accounting Changes

Change in Accounting Estimate

At the end of 2015, we changed the approach used to measure service and interest costs for pension and other postretirement benefits. In prior years, the Company measured service and interest costs utilizing a single weighted-average discount rate derived from the yield curve used to measure the plan obligations. For 2016, we measured service and interest costs by applying the specific spot rates along that yield curve to the plans’ liability cash flows. The Company believes this approach provides a more precise measurement of service and interest costs by aligning the timing of the plans’ liability cash flows to the corresponding spot rates on the yield curve. This change does not affect the measurement of our plan obligations. The Company has accounted for this change as a change in accounting estimate and, accordingly, has accounted for it on a prospective basis. The Company's adoption of the full yield curve approach will reduce 2016 service and interest cost by approximately $4.5 million ($2.8 million after-tax) as compared to the previous method.

New Accounting Pronouncements Adopted

Consolidation

In February 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2015-02, Consolidation (Topic 810) Amendments to the Consolidation Analysis, which amends the analysis required to determine whether to consolidate certain types of legal entities such as limited partnerships, limited liability corporations, and certain securitization structures. The new guidance was effective for us beginning in the first quarter of 2016. Application of the new guidance did not impact our financial statements or related disclosures.

Business Combinations

In September 2015, the FASB issued ASU 2015-16, Business Combinations (Topic 805), Simplifying the Accounting for Measurement-Period Adjustments, which requires the acquirer in a business combination to recognize measurement-period adjustments in the period in which it determines the amount of the adjustment. The new guidance was effective for us in the first quarter of 2016. Application of the new guidance did not impact our financial statements or related disclosures.

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 can adopt the new guidance using either the retrospective method or the cumulative effect transition method. We are evaluating the effect that the new guidance will have on our consolidated financial statements and related disclosures and when we will elect to adopt this standard.

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, using a modified retrospective transition method. We are evaluating the effect that the new guidance will have on our consolidated financial statements and related disclosures and when we will elect to adopt this standard.

Financial Instruments

In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall: 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.

Equity Method and Joint Ventures

In March 2016, the FASB issued 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 is effective for us in the first quarter of 2017 with early adoption permitted. We do not expect the new guidance to 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 payment accounting and presentation. The new guidance is effective for us in the first quarter of 2017 with early adoption permitted. We are evaluating the effect that the new guidance will have on our financial statements and related disclosures.