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Significant Accounting Policies (Policies) | 12 Months Ended
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Dec. 31, 2020
Accounting Policies [Abstract] |
Consolidation, Policy [Policy Text Block] | Principles of consolidation: The accompanying consolidated financial statements include Marten Transport, Ltd. and its subsidiaries. All intercompany accounts and transactions are eliminated upon consolidation.
Cash and Cash Equivalents, Policy [Policy Text Block] | Cash and cash equivalents: Cash in excess of current operating requirements is invested in short-term, highly liquid investments. We consider all highly liquid investments purchased with original maturities of three months or less to be cash equivalents. We maintain our cash and cash equivalents in bank accounts which, at times, may exceed federally insured limits. We have not experienced any losses in such accounts.
Receivable [Policy Text Block] | Trade accounts receivable: Trade accounts receivable are recorded at the invoiced amounts, net of an allowance for doubtful accounts. A considerable amount of judgment is required in assessing the realization of these receivables including the current creditworthiness of each customer and related aging of the past-due balances, including any billing disputes. In order to assess the collectibility of these receivables, we perform ongoing credit evaluations of our customers’ financial condition. Through these evaluations, we may become aware of a situation where a customer may not be able to meet its financial obligations due to deterioration of its financial viability, credit ratings or bankruptcy. The allowance for doubtful accounts is based on the best information available to us and is reevaluated and adjusted as additional information is received. We evaluate the allowance based on historical write-off experience, the size of the individual customer balances, past-due amounts and the overall national economy. We review the adequacy of our allowance for doubtful accounts monthly. Invoice balances over 30 days after the contractual due date are considered past due per our policy and are reviewed individually for collectibility. Initial payments by new customers are monitored for compliance with contractual terms. Account balances are charged off against the allowance after all means of collection have been exhausted and the potential recovery is considered remote.
Property, Plant and Equipment, Policy [Policy Text Block] | Property and equipment: Additions and improvements to property and equipment are capitalized at cost. Maintenance and repair expenditures are charged to operations. Gains and losses on disposals of revenue equipment are included in operations as they are a normal, recurring component of our operations. Depreciation is computed based on the cost of the asset, reduced by its estimated salvage value, using the straight-line method for financial reporting purposes. We begin depreciating assets in the month that each asset is placed in service and, therefore, is ready for its intended use, and depreciate each asset until it is taken out of service and available for sale. Accelerated methods are used for income tax reporting purposes. Following is a summary of estimated useful lives for financial reporting purposes:
|  | Years |
Tractors |  |  | 5 |  |
Trailers |  |  | 7 |  |
Refrigerated containers |  |  | 12 |  |
Service and other equipment |  | 3 | - | 15 |
Buildings and improvements |  | 20 | - | 40 |
In 2020, we replaced our company-owned tractors within an average of 4.1 years and our trailers within an average of 6.4 years after purchase. Our useful lives for depreciating tractors is five years, for trailers is seven years and for refrigerated containers is 12 years, with a 25% salvage value for tractors, a 35% salvage value for trailers and no salvage value for refrigerated containers. These salvage values are based upon the expected market values of the equipment after five years for tractors and seven years for trailers. Depreciation expense calculated in this manner approximates the continuing declining value of the revenue equipment, and continues at a consistent straight-line rate for units held beyond the normal replacement cycle. Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future net undiscounted cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less the costs to sell.
Tires In Service [Policy Text Block] | Tires in service: The cost of original equipment and replacement tires placed in service is capitalized. Amortization is calculated based on cost, less estimated salvage value, using the straight-line method over 24 months. Tire amortization, which is included within supplies and maintenance in our consolidated statements of operations, was $6.6 million in 2020, $6.9 million in 2019 and $7.0 million in 2018. The current portion of capitalized tires in service is included in prepaid expenses and other in the accompanying consolidated balance sheets. The long-term portion of capitalized tires in service and the estimated salvage value are included in revenue equipment in the accompanying consolidated balance sheets. The cost of recapping tires is charged to operations as incurred.
Income Tax, Policy [Policy Text Block] | Income taxes: Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. We have reflected the necessary deferred tax assets and liabilities in the accompanying consolidated balance sheets. We believe the future tax deductions will be realized principally through future reversals of existing taxable temporary differences and future taxable income. In the ordinary course of business there is inherent uncertainty in quantifying our income tax positions. We assess our income tax positions and record tax benefits for all years subject to examination based upon management’s evaluation of the facts, circumstances, and information available at the reporting dates. For those tax positions where it is more-likely-than-not that a tax benefit will be sustained, we have recorded the largest amount of tax benefit with a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. For those income tax positions where it is not more-likely-than-not that a tax benefit will be sustained, no tax benefit has been recognized in the financial statements. Potential accrued interest and penalties related to unrecognized tax benefits are recognized as a component of income tax expense.
Internal Replacements of Insurance Contracts, Policy [Policy Text Block] | Insurance and claims: We self-insure, in part, for losses relating to workers’ compensation, auto liability, general liability, cargo, and property damage claims, along with employees’ health insurance with varying risk retention levels. We are responsible for the first $1.0 million on each auto liability claim. We are also responsible for the first $750,000 on each workers’ compensation claim. We maintain insurance coverage for per-incident and total losses in excess of these risk retention levels in amounts we consider adequate based upon historical experience and our ongoing review. We reserve currently for the estimated cost of the uninsured portion of pending claims, including legal costs. These reserves are periodically evaluated and adjusted based on our evaluation of the nature and severity of outstanding individual claims and an estimate of future claims development based on historical development. Under agreements with our insurance carriers and regulatory authorities, we have $17.0 million in standby letters of credit to guarantee settlement of claims.
Revenue from Contract with Customer [Policy Text Block] | Revenue recognition: We account for our revenue in accordance with FASB ASC 606, Revenue from Contracts with Customers, which we adopted on January 1, 2018 using the modified retrospective method. The current revenue standard requires us to recognize revenue and related expenses within each of our four reporting segments over time, compared with our former policy in which we recorded revenue and related expenses on the date shipment of freight was completed. We account for revenue of our Intermodal and Brokerage segments and revenue on freight transported by independent contractors within our Truckload and Dedicated segments on a gross basis because we are the principal service provider controlling the promised service before it is transferred to each customer. We are primarily responsible for fulfilling the promise to provide each specified service to each customer. We bear the primary risk of loss in the event of cargo claims by our customers. We also have complete control and discretion in establishing the price for each specified service. Accordingly, all such revenue billed to customers is classified as operating revenue and all corresponding payments to carriers for transportation services we arrange in connection with brokerage and intermodal activities and to independent contractor providers of revenue equipment are classified as purchased transportation expense within our consolidated statements of operations. See Note 17 for more information. Our largest customer, Walmart, accounted for 24% of our revenue in 2020 and 24% of our trade receivables as of December 31, 2020, 17% of our revenue in 2019 and 21% of our trade receivables as of December 31, 2019 and 15% of our revenue in 2018. Our second largest customer, The Coca-Cola Company, accounted for 12% of our revenue in 2020 and 8% of our trade receivables as of December 31, 2020, 14% of our revenue in 2019 and 9% of our trade receivables as of December 31, 2019 and 13% of our revenue in 2018. During each of 2020, 2019 and 2018, approximately 99% of our revenue was generated within the United States.
Share-based Payment Arrangement [Policy Text Block] | Share-based payment arrangement compensation: Under our stock incentive plans, all of our employees and any subsidiary employees, as well as all of our non-employee directors, may be granted stock-based awards, including incentive and non-statutory stock options and performance unit awards. We account for share-based payment arrangements in accordance with FASB ASC 718, Compensation-Stock Compensation, which requires all share-based payments to employees and non-employee directors, including grants of employee stock options and performance unit awards, to be recognized in the income statement based on their fair values at the date of grant.
Earnings Per Share, Policy [Policy Text Block] | Earnings per common share: Basic earnings per common share is computed by dividing net income by the weighted average number of common shares outstanding during the year. Diluted earnings per common share is computed by dividing net income by the sum of the weighted average number of common shares outstanding plus all additional common shares that would have been outstanding if potentially dilutive common shares related to stock options and performance unit awards had been issued using the treasury stock method.
Segment Reporting, Policy [Policy Text Block] | Segment reporting: We report our operating segments in accordance with accounting standards codified in FASB ASC 280, Segment Reporting. We have five current operating segments that are aggregated into four reporting segments (Truckload, Dedicated, Intermodal and Brokerage) for financial reporting purposes. See Note 17 for more information.
Use of Estimates, Policy [Policy Text Block] | Use of estimates: We must make estimates and assumptions to prepare the consolidated financial statements in conformity with U.S. generally accepted accounting principles. These estimates and assumptions affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities in the consolidated financial statements and the reported amount of revenue and expenses during the reporting period. These estimates are primarily related to insurance and claims accruals and depreciation. Ultimate results could differ from these estimates.

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- Definition Disclosure of accounting policy for cash and cash equivalents, including the policy for determining which items are treated as cash equivalents. Other information that may be disclosed includes (1) the nature of any restrictions on the entity's use of its cash and cash equivalents, (2) whether the entity's cash and cash equivalents are insured or expose the entity to credit risk, (3) the classification of any negative balance accounts (overdrafts), and (4) the carrying basis of cash equivalents (for example, at cost) and whether the carrying amount of cash equivalents approximates fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4273-108586 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 + Details
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- Definition Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=109239629&loc=d3e5614-111684 + Details
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