ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION (Policies)	12 Months Ended
	Dec. 31, 2017
ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION
Consolidation	Consolidation: The consolidated financial statements include the accounts of the Company and its subsidiaries. All significant intercompany accounts and transactions are eliminated in consolidation.
Segment Information	Segment Information: The Company uses the “management approach” for determining its reportable segment information. The management approach is based on the way management organizes the reportable segments within the Company for making operating decisions and assessing performance. See Note M for further discussion of segment reporting.
Use of Estimates	Use of Estimates: The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual amounts may differ from those estimates.
Reclassifications	Reclassifications: Certain reclassifications have been made to the prior years’ consolidated financial statements to conform to the current year presentation. The insurance receivable for the amount of workers’ compensation and third-party casualty claims in excess of self-insurance retention limits, which was previously offset against the reserve included in accrued expenses, has been reclassed to other accounts receivable, resulting in an $8.7 million increase in other accounts receivable and a corresponding increase in accrued expenses in the consolidated balance sheet at December 31, 2016. Amounts totaling $18.6 million related to certain service centers of the Company’s Asset-Based operations previously recorded in leasehold improvements were reclassed to land and structures in the consolidated balance sheet at December 31, 2016. These reclassifications were previously reported in the Company’s first quarter 2017 Quarterly Report on Form 10-Q. The prior period impact of the reclassification of the insurance receivable is also reflected in the consolidated statements of cash flows for the years ended December 31, 2016 and 2015. Reclassifications were also made to the consolidated financial statements to apply the provisions of accounting pronouncements adopted during the first quarter of 2017 related to deferred income taxes, share-based compensation, and cash flow classification (see Adopted Accounting Pronouncements within Note B). The Company’s deferred tax assets were reclassed, by jurisdiction, from current to long-term in the consolidated balance sheets. The net change in restricted cash previously presented in financing activities of the Company’s consolidated statements of cash flows was removed and restricted cash was included in the reconciliation of beginning- and end-of-period totals of cash and cash equivalents and restricted cash. Cash paid by the Company when directly withholding shares from an employee’s share-based compensation award for tax-withholding purposes was reclassified from an operating activity within changes in income taxes to a financing activity in the consolidated statements of cash flows. There was no impact on the Company’s consolidated revenues, operating expenses, operating income, or earnings per share as a result of the reclassifications. During the third quarter of 2017, the Company modified the presentation of segment expenses allocated from shared services. Previously, expenses allocated from company-wide functions were categorized in individual segment expense line items by type of expense. Allocated expenses are now presented on a single shared services line within the Company’s operating segment disclosures. Reclassifications have been made to the prior period operating segment expenses to conform to the current year presentation. There was no impact on each segment’s total expenses as a result of the reclassifications.