Summary of Significant Accounting Policies	12 Months Ended
Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned and majority-owned subsidiaries. All significant intercompany transactions and accounts have been eliminated. Use of Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates, and such differences could be material. Significant estimates include useful lives of property and equipment and related salvage value, claims reserves for liability and workers’ compensation claims and valuation allowance for deferred tax assets. Cash and Cash Equivalents Cash and cash equivalents include all highly liquid investment instruments with an original maturity of three months or less. Customer Receivables and Allowances Customer receivables are recorded at the invoiced amount, net of allowances for uncollectible accounts and revenue adjustments. The allowances for uncollectible accounts and revenue adjustments are based on historical experience as well as any known trends or uncertainties related to customer billing and account collectability. The Company reviews the adequacy of its allowance for doubtful accounts on a quarterly basis. Past due balances over contractual payment terms and exceeding specified amounts are reviewed individually for collectability. Receivable balances are written off when collection is deemed unlikely. Operating Supplies Operating supplies consist primarily of parts, materials and supplies for servicing the Company’s revenue and service equipment. Operating supplies are recorded at the lower of cost (on a first-in, first-out basis) or market. Tires purchased as part of revenue and service equipment are capitalized as part of the cost of the equipment. Replacement tires are charged to expense when placed in service. Assets Held for Sale Assets held for sale are comprised primarily of revenue equipment no longer being utilized in continuing operations which are available and ready for sale. Assets held for sale are no longer subject to depreciation and are recorded at the lower of depreciated book value or fair market value less selling costs. The Company expects to sell these assets within the next twelve months. At December 31, 2019, assets held for sale was comprised of revenue equipment and a terminal. At December 31, 2018, assets held for sale included revenue equipment of approximately $5.2 million and assets of a business held for sale of approximately $28.0 million. See Note 4, Divesture of Xpress International for more discussion related to the sale of our interest in Xpress Internacional S.A. de C.V. (Xpress Internacional) during January 2019. Property and Equipment Property and equipment are carried at cost. Depreciation of property and equipment is computed using the straight-line method for financial reporting purposes and accelerated methods for tax purposes over the estimated useful lives of the related assets (net of salvage values ranging from 25.0% to 50.0% of revenue equipment). The Company periodically evaluates the estimated useful lives and salvage values of its revenue equipment, due to changes in business needs and expected usage of the equipment. Upon the retirement of property and equipment, the related asset cost and accumulated depreciation are removed from the accounts and any gain or loss is included in depreciation and amortization expense in the Company’s consolidated statements of comprehensive income. Expenditures for normal maintenance and repairs are expensed. Renewals or betterments that affect the nature of an asset or increase its useful life are capitalized. Leases We determine if an arrangement is a lease or contains a lease at inception and perform an analysis to determine whether the lease is an operating lease or a finance lease. We measure right-of-use (“ROU”) assets and lease liabilities at the lease commencement date based on the present value of the remaining lease payments. As most of our leases do not provide a readily determinable implicit rate, we estimate an incremental borrowing rate based on the credit quality of the Company and by comparing interest rates available in the market for similar borrowings, and adjusting this amount based on the impact of collateral over the term of each lease. We use this rate to discount the remaining lease payments in measuring the ROU asset and lease liability. We use the implicit rate when readily determinable. We recognize lease expense for operating leases on a straight-line basis over the lease term. For our finance leases, we recognize amortization expense from the amortization of the ROU asset and interest expense on the related lease liability. We do not separate lease and nonlease components of contracts, except for certain leased information technology assets that are embedded within various service agreements. The lease components included in those agreements are included in the ROU asset and lease liability, and the amounts are not significant. Leases with an initial term of twelve months or less are not recorded on the consolidated balance sheet. We recognize lease expense for these leases on a straight-line basis over the lease term. Impairment of Long Lived Assets The Company reviews its long-lived assets, including property and equipment, for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Expected future cash flows are used to analyze whether an impairment has occurred. If the sum of the expected undiscounted cash flows is less than the carrying value of the long-lived asset, then an impairment loss is recognized. We measure the impairment loss by comparing the fair value of the asset to its carrying value. Fair value is determined based on a discounted cash flow analysis or the appraised value of the assets, as appropriate. Goodwill In 2013, the Company adopted Accounting Standards Update (ASU) 2011-08, Testing Goodwill for Impairment, which allows companies to first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. Under this standard, the Company would not be required to calculate the fair value of a reporting unit unless the Company determines, based on the qualitative review, that it is more likely than not that its fair value is less than its carrying amount. The standard includes events and circumstances for the Company to consider when conducting the qualitative assessment. The quantitative impairment test consists of two different steps. The first step identifies potential impairment by comparing the fair value of a reporting unit with its carrying amount, including goodwill. If the fair value exceeds its carrying amount, goodwill is not considered impaired and the second step of the test is unnecessary. If the carrying amount of a reporting unit’s goodwill exceeds its fair value, the second step measures the impairment loss, if any. The second step compares the implied fair value of goodwill with the carrying amount of that goodwill. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination. If the carrying amount of goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in an amount equal to that excess. The Company performs an annual goodwill impairment analysis at the reporting unit level as of October 1 each year or when an event occurs which might cause or indicate impairment. The Company performed the qualitative assessment in the fourth quarter of 2019 and 2018 and concluded it was more likely than not that the fair value of the Truckload reporting unit was greater than its carrying amount. Intangible Assets Customer relationships are valued as part of acquisition-related transactions using the income appraisal methodology. The income appraisal methodology includes a determination of the present value of future monetary benefits to be derived from the anticipated income, or ownership, of the subject asset. The value of customer relationships includes the value expected to be realized from existing contracts as well as from expected renewals of such contracts and is calculated using unweighted and weighted total undiscounted cash flows as part of the income appraisal methodology. Customer relationships are amortized over seven to fifteen years. The Company tests intangible assets with definite lives for impairment if conditions exist that indicate the carrying value may not be recoverable. There was no impairment of customer relationships in 2019 and 2018. Trade names are valued based on various factors including the projected revenue stream associated with the intangible asset. The Company’s trade names have an indefinite life and are not amortized. In the fourth quarter of 2019 and 2018, the Company performed the qualitative assessment of its trade name assets and concluded it was more likely than not that the fair value of each of the assets is greater than its carrying amount. Therefore, the Company concluded it was not necessary to perform the quantitative impairment test. Book Overdraft Book overdraft represents outstanding checks in excess of current cash levels. The Company funds its book overdraft from its line of credit and operating cash flows. Deferred Financing Costs The Company presents debt issuance costs as a direct deduction from the related debt, consistent with debt discounts. Debt issuance costs associated with revolving line-of-credit arrangements are presented as an asset. All such debt issuance costs are amortized ratably over the term of the arrangement. Term loan debt issuance costs excluding original issue discount, net of accumulated amortization were $1.2 million and $1.3 million at December 31, 2019 and 2018, respectively. Revolver gross debt issuance costs were $1.5 million at December 31, 2019 and 2018, offset by accumulated amortization of $0.5 million and $0.2 million at December 31, 2019 and 2018, respectively. Debt issuance cost amortization expense excluding original issue discount was $0.3 million, $1.6 million and $3.4 million in 2019, 2018 and 2017, respectively. Recognition of Revenue The Company generates revenues primarily from shipments executed by the Company’s Truckload and Brokerage operations. Those shipments are the Company’s performance obligations, arising under contracts we have entered into with customers. Under such contracts, revenue is recognized when obligations are satisfied, which occurs over time with the transit of shipments from origin to destination. This is appropriate as the customer simultaneously receives and consumes the benefits as the Company performs its obligation. Revenue is measured as the amount of consideration the Company expects to receive in exchange for providing services. The most significant judgment used in recognition of revenue is the determination of miles driven as the basis for determining the amount of revenue to be recognized for partially fulfilled obligations. Accessorial charges for fuel surcharge, loading and unloading, stop charges, and other immaterial charges are part of the consideration we receive for the single performance obligation of delivering shipments. Contracts entered into with our customers do not contain material financing components. The majority of revenue contracts with our customers have a duration of one year or less and do not require any significant start-up costs, and as such, costs incurred to obtain contracts associated with these contracts are expensed as incurred. For contracts with durations exceeding one year, incremental start-up costs are capitalized and amortized on a straight line basis over the contract period which materially represents the period of revenue generation. Incremental capitalized start-up costs totaled $3.2 million and $3.3 million at December 31, 2019 and 2018, respectively, and are included in other current assets in our consolidated balance sheets. Amortization expense associated with our start up costs was $1.5 million and $1.2 million in 2019 and 2018, respectively. Through the Company’s Brokerage operations, the Company outsources the transportation of the loads to third-party carriers. The Company is a principal in these arrangements, and therefore records revenue associated with these contracts on a gross basis. The Company has the primary responsibility to meet the customer’s requirements. The Company invoices and collects from its customers and also maintains discretion over pricing. Additionally, the Company is responsible for selection of third-party transportation providers to the extent used to satisfy customer freight requirements. The timing of revenue recognition, billings, cash collections, and allowance for doubtful accounts results in billed and unbilled receivables on our consolidated balance sheet. The Company receives the unconditional right to bill when shipments are delivered to their destination. We generally receive payment within 40 days of completion of performance obligations. Unbilled receivables recorded on the consolidated balance sheet were $2.7 million and $2.9 million at December 31, 2019 and 2018, respectively and are included in customer receivables in the consolidated balance sheets. Income Taxes Income taxes are accounted for under the asset-and-liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statements carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. 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 as income or expense in the period that includes the enactment date. The Company evaluates the need for a valuation allowance on deferred tax assets based on whether it believes that it is more likely than not all deferred tax assets will be realized. A consideration of future taxable income is made as well as on-going prudent feasible tax planning strategies in assessing the need for valuation allowances. In the event it is determined all or part of a deferred tax asset would not be able to be realized, management would record an adjustment to the deferred tax asset and recognize a charge against income at that time. The Company’s estimate of the potential outcome of any uncertain tax issue is subject to its assessment of relevant risks, facts and circumstances existing at that time. The Company accounts for uncertain tax positions in accordance with ASC 740, Income Taxes, and records a liability when such uncertainties meet the more likely than not recognition threshold. Potential accrued interest and penalties related to unrecognized tax benefits are recognized as a component of income tax expense. Concentration of Credit Risk Concentrations of credit risk with respect to customer receivables are limited due to the large number of entities comprising the Company’s customer base and their dispersion across many different industries. Revenues from the Company’s largest customer accounted for 12.3% of total consolidated revenues before fuel surcharge during 2019. The Company performs ongoing credit evaluations and generally does not require collateral. Stock-Based Compensation The Company has stock-based compensation plans that provide for grants of equity to its management in the form of stock options, stock appreciation rights, stock awards, restricted stock units, performance awards, performance units, and any other form established by the Compensation Committee. Stock-based compensation is recognized over the period for which an employee is required to provide service in exchange for the award. Stock-based compensation expense is included in salaries, wages, and benefits in the consolidated statements of comprehensive income. Claims and Insurance Accruals Claims and insurance accruals consist of cargo loss, physical damage, group health, liability (personal injury and property damage) and workers’ compensation claims and associated legal and other expenses within the Company’s established retention levels. Claims in excess of retention levels are generally covered by insurance in amounts the Company considers adequate. Claims accruals represent the uninsured portion of the loss and if we are the primary obligor, the insured portion of pending claims at December 31, 2019 and 2018, plus an estimated liability for incurred but not reported claims and the associated expense. Accruals for cargo loss, physical damage, group health, liability and workers’ compensation claims are estimated based on the Company’s evaluation of the type and severity of individual claims and future development based on historical trends. At December 31, 2019 and 2018, the amount recorded for both workers’ compensation and auto liability were based in part upon actuarial studies performed by a third-party actuary. At December 31, 2019 and 2018, the Company had a claim accrual and corresponding receivable for the amount above its self-insured retention of $0.4 million, which the Company believes should be sufficient to resolve the remaining claims. The Company believes the insurers will provide their portion of the remaining claims. Recently Issued Accounting Standards In June 2016, the FASB issued ASU No. 2016-13 Financial Instruments -Credit Losses (Topic 326) amending how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance requires the application of a current expected credit loss model, which is a new impairment model based on expected losses. The new guidance is effective for interim and annual reporting periods beginning after December 15, 2019, with early adoption permitted. The Company believes the adoption of this guidance will not have a material impact on its financial statements. In January 2017, the FASB issued ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment,” which eliminates Step 2 from the goodwill impairment testing process. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount. Under the new standard, a goodwill impairment loss is measured as the excess of the carrying value of a reporting unit over its fair value. The provisions of this update are effective for fiscal years beginning after December 15, 2019. The Company has evaluated the provisions of the pronouncement and does not expect the adoption of this guidance will have a material impact on the consolidated financial statements. On December 18, 2019, the FASB issued ASU 2019-12, which modifies ASC 740 to simplify the accounting for income taxes. The amendments in ASU 2019-12 are effective for public business entities for fiscal years beginning after December 15, 2020, including interim periods therein. Early adoption of the standard is permitted, including adoption in interim or annual periods for which financial statements have not yet been issued. The Company has not early adopted this guidance and will continue to evaluate the impact on its financial statements. Recently Adopted Accounting Standards In February 2016, the FASB issued ASU 2016‑02, “Leases (Topic 842),” and has subsequently issued supplemental and/or clarifying ASUs (collectively “ASC 842”), in order to increase transparency and comparability by recognizing lease assets and liabilities on the balance sheet and disclosing key information about leasing arrangements. We adopted ASC 842 using the modified retrospective approach and applied the transition provisions with an effective date as of January 1, 2019 for leases that existed on that date. Prior period results continue to be presented under ASC 840 based on the accounting originally in effect for such periods. We elected the “package of practical expedients” under ASC 842 which permits us to not reassess our historical assessments of (1) whether contracts are or contain leases, (2) lease classification and (3) initial direct costs. We also elected the practical expedient to not reassess certain land easements. We did not elect the use-of-hindsight practical expedient during the transition of ASC 842. Adoption of ASC 842 resulted in the recording of operating lease ROU assets and corresponding operating lease liabilities of approximately $183.0 million. The adoption of ASC 842 also resulted in increased disclosure, including qualitative and quantitative disclosures about the nature, amount, timing, and uncertainty of cash flows arising from leases. See the “Leases” section of this note and Note 10, Leases for additional information.

2. Summary of Significant Accounting Policies

Principles of Consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned and majority-owned subsidiaries. All significant intercompany transactions and accounts have been eliminated.

Use of Estimates in the Preparation of Financial Statements

The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates, and such differences could be material. Significant estimates include useful lives of property and equipment and related salvage value, claims reserves for liability and workers’ compensation claims and valuation allowance for deferred tax assets.

Cash and Cash Equivalents

Cash and cash equivalents include all highly liquid investment instruments with an original maturity of three months or less.

Customer Receivables and Allowances

Customer receivables are recorded at the invoiced amount, net of allowances for uncollectible accounts and revenue adjustments. The allowances for uncollectible accounts and revenue adjustments are based on historical experience as well as any known trends or uncertainties related to customer billing and account collectability. The Company reviews the adequacy of its allowance for doubtful accounts on a quarterly basis. Past due balances over contractual payment terms and exceeding specified amounts are reviewed individually for collectability. Receivable balances are written off when collection is deemed unlikely.

Operating Supplies

Operating supplies consist primarily of parts, materials and supplies for servicing the Company’s revenue and service equipment. Operating supplies are recorded at the lower of cost (on a first-in, first-out basis) or market. Tires purchased as part of revenue and service equipment are capitalized as part of the cost of the equipment. Replacement tires are charged to expense when placed in service.

Assets Held for Sale

Assets held for sale are comprised primarily of revenue equipment no longer being utilized in continuing operations which are available and ready for sale. Assets held for sale are no longer subject to depreciation and are recorded at the lower of depreciated book value or fair market value less selling costs. The Company expects to sell these assets within the next twelve months. At December 31, 2019, assets held for sale was comprised of revenue equipment and a terminal. At December 31, 2018, assets held for sale included revenue equipment of approximately $5.2 million and assets of a business held for sale of approximately $28.0 million. See Note 4, Divesture of Xpress International for more discussion related to the sale of our interest in Xpress Internacional S.A. de C.V. (Xpress Internacional) during January 2019.

Property and Equipment

Property and equipment are carried at cost. Depreciation of property and equipment is computed using the straight-line method for financial reporting purposes and accelerated methods for tax purposes over the estimated useful lives of the related assets (net of salvage values ranging from 25.0% to 50.0% of revenue equipment). The Company periodically evaluates the estimated useful lives and salvage values of its revenue equipment, due to changes in business needs and expected usage of the equipment. Upon the retirement of property and equipment, the related asset cost and accumulated depreciation are removed from the accounts and any gain or loss is included in depreciation and amortization expense in the Company’s consolidated statements of comprehensive income. Expenditures for normal maintenance and repairs are expensed. Renewals or betterments that affect the nature of an asset or increase its useful life are capitalized.

Leases

We determine if an arrangement is a lease or contains a lease at inception and perform an analysis to determine whether the lease is an operating lease or a finance lease. We measure right-of-use (“ROU”) assets and lease liabilities at the lease commencement date based on the present value of the remaining lease payments. As most of our leases do not provide a readily determinable implicit rate, we estimate an incremental borrowing rate based on the credit quality of the Company and by comparing interest rates available in the market for similar borrowings, and adjusting this amount based on the impact of collateral over the term of each lease. We use this rate to discount the remaining lease payments in measuring the ROU asset and lease liability. We use the implicit rate when readily determinable. We recognize lease expense for operating leases on a straight-line basis over the lease term. For our finance leases, we recognize amortization expense from the amortization of the ROU asset and interest expense on the related lease liability. We do not separate lease and nonlease components of contracts, except for certain leased information technology assets that are embedded within various service agreements. The lease components included in those agreements are included in the ROU asset and lease liability, and the amounts are not significant.

Leases with an initial term of twelve months or less are not recorded on the consolidated balance sheet. We recognize lease expense for these leases on a straight-line basis over the lease term.

Impairment of Long Lived Assets

The Company reviews its long-lived assets, including property and equipment, for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Expected future cash flows are used to analyze whether an impairment has occurred. If the sum of the expected undiscounted cash flows is less than the carrying value of the long-lived asset, then an impairment loss is recognized. We measure the impairment loss by comparing the fair value of the asset to its carrying value. Fair value is determined based on a discounted cash flow analysis or the appraised value of the assets, as appropriate.

Goodwill

In 2013, the Company adopted Accounting Standards Update (ASU) 2011-08, Testing Goodwill for Impairment, which allows companies to first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. Under this standard, the Company would not be required to calculate the fair value of a reporting unit unless the Company determines, based on the qualitative review, that it is more likely than not that its fair value is less than its carrying amount. The standard includes events and circumstances for the Company to consider when conducting the qualitative assessment.

The quantitative impairment test consists of two different steps. The first step identifies potential impairment by comparing the fair value of a reporting unit with its carrying amount, including goodwill. If the fair value exceeds its carrying amount, goodwill is not considered impaired and the second step of the test is unnecessary. If the carrying amount of a reporting unit’s goodwill exceeds its fair value, the second step measures the impairment loss, if any. The second step compares the implied fair value of goodwill with the carrying amount of that goodwill. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination. If the carrying amount of goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in an amount equal to that excess.

The Company performs an annual goodwill impairment analysis at the reporting unit level as of October 1 each year or when an event occurs which might cause or indicate impairment. The Company performed the qualitative assessment in the fourth quarter of 2019 and 2018 and concluded it was more likely than not that the fair value of the Truckload reporting unit was greater than its carrying amount.

Intangible Assets

Customer relationships are valued as part of acquisition-related transactions using the income appraisal methodology. The income appraisal methodology includes a determination of the present value of future monetary benefits to be derived from the anticipated income, or ownership, of the subject asset. The value of customer relationships includes the value expected to be realized from existing contracts as well as from expected renewals of such contracts and is calculated using unweighted and weighted total undiscounted cash flows as part of the income appraisal methodology. Customer relationships are amortized over seven to fifteen years. The Company tests intangible assets with definite lives for impairment if conditions exist that indicate the carrying value may not be recoverable. There was no impairment of customer relationships in 2019 and 2018.

Trade names are valued based on various factors including the projected revenue stream associated with the intangible asset. The Company’s trade names have an indefinite life and are not amortized. In the fourth quarter of 2019 and 2018, the Company performed the qualitative assessment of its trade name assets and concluded it was more likely than not that the fair value of each of the assets is greater than its carrying amount. Therefore, the Company concluded it was not necessary to perform the quantitative impairment test.

Book Overdraft

Book overdraft represents outstanding checks in excess of current cash levels. The Company funds its book overdraft from its line of credit and operating cash flows.

Deferred Financing Costs

The Company presents debt issuance costs as a direct deduction from the related debt, consistent with debt discounts. Debt issuance costs associated with revolving line-of-credit arrangements are presented as an asset. All such debt issuance costs are amortized ratably over the term of the arrangement. Term loan debt issuance costs excluding original issue discount, net of accumulated amortization were $1.2 million and $1.3 million at December 31, 2019 and 2018, respectively. Revolver gross debt issuance costs were $1.5 million at December 31, 2019 and 2018, offset by accumulated amortization of $0.5 million and $0.2 million at December 31, 2019 and 2018, respectively. Debt issuance cost amortization expense excluding original issue discount was $0.3 million, $1.6 million and $3.4 million in 2019, 2018 and 2017, respectively.

Recognition of Revenue

The Company generates revenues primarily from shipments executed by the Company’s Truckload and Brokerage operations. Those shipments are the Company’s performance obligations, arising under contracts we have entered into with customers. Under such contracts, revenue is recognized when obligations are satisfied, which occurs over time with the transit of shipments from origin to destination. This is appropriate as the customer simultaneously receives and consumes the benefits as the Company performs its obligation. Revenue is measured as the amount of consideration the Company expects to receive in exchange for providing services. The most significant judgment used in recognition of revenue is the determination of miles driven as the basis for determining the amount of revenue to be recognized for partially fulfilled obligations. Accessorial charges for fuel surcharge, loading and unloading, stop charges, and other immaterial charges are part of the consideration we receive for the single performance obligation of delivering shipments. Contracts entered into with our customers do not contain material financing components.

The majority of revenue contracts with our customers have a duration of one year or less and do not require any significant start-up costs, and as such, costs incurred to obtain contracts associated with these contracts are expensed as incurred. For contracts with durations exceeding one year, incremental start-up costs are capitalized and amortized on a straight line basis over the contract period which materially represents the period of revenue generation. Incremental capitalized start-up costs totaled $3.2 million and $3.3 million at December 31, 2019 and 2018, respectively, and are included in other current assets in our consolidated balance sheets. Amortization expense associated with our start up costs was $1.5 million and $1.2 million in 2019 and 2018, respectively.

Through the Company’s Brokerage operations, the Company outsources the transportation of the loads to third-party carriers. The Company is a principal in these arrangements, and therefore records revenue associated with these contracts on a gross basis. The Company has the primary responsibility to meet the customer’s requirements. The Company invoices and collects from its customers and also maintains discretion over pricing. Additionally, the Company is responsible for selection of third-party transportation providers to the extent used to satisfy customer freight requirements.

The timing of revenue recognition, billings, cash collections, and allowance for doubtful accounts results in billed and unbilled receivables on our consolidated balance sheet. The Company receives the unconditional right to bill when shipments are delivered to their destination. We generally receive payment within 40 days of completion of performance obligations. Unbilled receivables recorded on the consolidated balance sheet were $2.7 million and $2.9 million at December 31, 2019 and 2018, respectively and are included in customer receivables in the consolidated balance sheets.

Income Taxes

Income taxes are accounted for under the asset-and-liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statements carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. 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 as income or expense in the period that includes the enactment date.

The Company evaluates the need for a valuation allowance on deferred tax assets based on whether it believes that it is more likely than not all deferred tax assets will be realized. A consideration of future taxable income is made as well as on-going prudent feasible tax planning strategies in assessing the need for valuation allowances. In the event it is determined all or part of a deferred tax asset would not be able to be realized, management would record an adjustment to the deferred tax asset and recognize a charge against income at that time.

The Company’s estimate of the potential outcome of any uncertain tax issue is subject to its assessment of relevant risks, facts and circumstances existing at that time. The Company accounts for uncertain tax positions in accordance with ASC 740, Income Taxes, and records a liability when such uncertainties meet the more likely than not recognition threshold. Potential accrued interest and penalties related to unrecognized tax benefits are recognized as a component of income tax expense.

Concentration of Credit Risk

Concentrations of credit risk with respect to customer receivables are limited due to the large number of entities comprising the Company’s customer base and their dispersion across many different industries. Revenues from the Company’s largest customer accounted for 12.3% of total consolidated revenues before fuel surcharge during 2019. The Company performs ongoing credit evaluations and generally does not require collateral.

Stock-Based Compensation

The Company has stock-based compensation plans that provide for grants of equity to its management in the form of stock options, stock appreciation rights, stock awards, restricted stock units, performance awards, performance units, and any other form established by the Compensation Committee. Stock-based compensation is recognized over the period for which an employee is required to provide service in exchange for the award. Stock-based compensation expense is included in salaries, wages, and benefits in the consolidated statements of comprehensive income.

Claims and Insurance Accruals

Claims and insurance accruals consist of cargo loss, physical damage, group health, liability (personal injury and property damage) and workers’ compensation claims and associated legal and other expenses within the Company’s established retention levels. Claims in excess of retention levels are generally covered by insurance in amounts the Company considers adequate. Claims accruals represent the uninsured portion of the loss and if we are the primary obligor, the insured portion of pending claims at December 31, 2019 and 2018, plus an estimated liability for incurred but not reported claims and the associated expense. Accruals for cargo loss, physical damage, group health, liability and workers’ compensation claims are estimated based on the Company’s evaluation of the type and severity of individual claims and future development based on historical trends. At December 31, 2019 and 2018, the amount recorded for both workers’ compensation and auto liability were based in part upon actuarial studies performed by a third-party actuary.

At December 31, 2019 and 2018, the Company had a claim accrual and corresponding receivable for the amount above its self-insured retention of $0.4 million, which the Company believes should be sufficient to resolve the remaining claims. The Company believes the insurers will provide their portion of the remaining claims.

Recently Issued Accounting Standards

In June 2016, the FASB issued ASU No. 2016-13 Financial Instruments -Credit Losses (Topic 326) amending how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance requires the application of a current expected credit loss model, which is a new impairment model based on expected losses. The new guidance is effective for interim and annual reporting periods beginning after December 15, 2019, with early adoption permitted. The Company believes the adoption of this guidance will not have a material impact on its financial statements.

In January 2017, the FASB issued ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment,” which eliminates Step 2 from the goodwill impairment testing process. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount. Under the new standard, a goodwill impairment loss is measured as the excess of the carrying value of a reporting unit over its fair value. The provisions of this update are effective for fiscal years beginning after December 15, 2019. The Company has evaluated the provisions of the pronouncement and does not expect the adoption of this guidance will have a material impact on the consolidated financial statements.

On December 18, 2019, the FASB issued ASU 2019-12, which modifies ASC 740 to simplify the accounting for income taxes. The amendments in ASU 2019-12 are effective for public business entities for fiscal years beginning after December 15, 2020, including interim periods therein. Early adoption of the standard is permitted, including adoption in interim or annual periods for which financial statements have not yet been issued. The Company has not early adopted this guidance and will continue to evaluate the impact on its financial statements.

Recently Adopted Accounting Standards

In February 2016, the FASB issued ASU 2016‑02, “Leases (Topic 842),” and has subsequently issued supplemental and/or clarifying ASUs (collectively “ASC 842”), in order to increase transparency and comparability by recognizing lease assets and liabilities on the balance sheet and disclosing key information about leasing arrangements. We adopted ASC 842 using the modified retrospective approach and applied the transition provisions with an effective date as of January 1, 2019 for leases that existed on that date. Prior period results continue to be presented under ASC 840 based on the accounting originally in effect for such periods. We elected the “package of practical expedients” under ASC 842 which permits us to not reassess our historical assessments of (1) whether contracts are or contain leases, (2) lease classification and (3) initial direct costs. We also elected the practical expedient to not reassess certain land easements. We did not elect the use-of-hindsight practical expedient during the transition of ASC 842. Adoption of ASC 842 resulted in the recording of operating lease ROU assets and corresponding operating lease liabilities of approximately $183.0 million. The adoption of ASC 842 also resulted in increased disclosure, including qualitative and quantitative disclosures about the nature, amount, timing, and uncertainty of cash flows arising from leases. See the “Leases” section of this note and Note 10, Leases for additional information.