Summary of Significant Accounting Policies (Policies)	3 Months Ended	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2018	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation, Policy		The condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. As a result, certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) have been condensed or omitted. The Company believes that the disclosures made are adequate to make the information presented not misleading. The condensed consolidated financial statements reflect all adjustments, consisting of normal recurring items, which are, in the opinion of management, necessary to a fair statement of the results for the interim periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company's Form 10-K as filed with the Securities and Exchange Commission on February 23, 2018. All significant intercompany accounts and transactions have been eliminated in consolidation. All dollar amounts in the notes are presented in thousands except for per share data or unless otherwise specified.
Revenue Recognition, Policy	Effective January 1, 2018, revenue is recognized upon transfer of control of promised services to customers, which occurs over time. The Company has determined that in general each shipment transaction or service order constitutes a separate contract with the customer. However, when the Company provides multiple services to a customer, different contracts may be present for different services. The Company combines the contracts, which form a single performance obligation, and accounts for the contracts as a single contract when certain criteria are met. The Company typically satisfies its performance obligations as services are rendered over time. A typical shipment would include services rendered at origin, such as pick-up and delivery to port, freight services from origin to destination port and destination services, such as customs clearance and final delivery. The Company measures the performance of its obligations as services are completed over the life of a shipment, including services at origin, freight and destination. This method of measurement of progress depicts the pattern of the Company's actual performance under the contracts with the customer. There are no significant judgments involved in measuring the progress of the performance obligations. Amounts allocated to the services for each performance obligation are typically based on standalone selling prices. The Company does not have significant variable consideration in its contracts. Taxes assessed concurrently with a specific revenue-producing transaction that are collected by the Company from a customer are excluded from revenue. Typically, transaction prices for each of the Company's services are quoted as separate components; however, customers on occasion will request an all-inclusive rate for a set of services known in the industry as “door-to-door service.” This means that the customer is billed a single rate for all services from pickup at origin to delivery at destination. In these instances, the transaction price is allocated to each service on a relative selling price basis. The Company fulfills nearly all of its performance obligations within a one to two month-period and contracts with customers have an original expected duration of less than one year. The Company generally has an unconditional right to consideration when the services are initiated or soon thereafter. The amount due from the customer is recorded as accounts receivable. The amounts related to services that are not yet completed at the reporting date are presented as contract liabilities, with corresponding direct costs to fulfill the performance obligation that will be satisfied in the future presented as deferred contract costs. The Company generally does not incur incremental costs to obtain the contract with the customer. The Company may incur costs to fulfill the contract with the customers, such as set-up costs. However, the amount incurred is insignificant to the Company’s consolidated financial statements. The Company evaluates whether amounts billed to customers should be reported as gross or net revenue. Generally, revenue is recorded on a gross basis when the Company is primarily responsible for fulfilling the promise to provide the services, when it assumes risk of loss, when it has discretion in setting the prices for the services to the customers, and when the Company has the ability to direct the use of the services provided by the third party.
Accounts Receivable, Policy		The Company maintains an allowance for doubtful accounts, which is reviewed at least monthly for estimated losses resulting from the inability of its customers to make required payments for services and advances. Additional allowances may be necessary in the future if the ability of customers to pay deteriorates. The Company has recorded an allowance for doubtful accounts in the amounts of $12,272 as of June 30, 2018 and $12,858 as of December 31, 2017. Additions and write-offs have not been significant in the periods presented.
Use of Estimates, Policy		The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of the assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the period. The Company uses estimates primarily in the following areas: accounts receivable valuation, accrual of costs related to ancillary services the Company provides, accrual of liabilities for the portion of the related exposure that the Company has self-insured, accrual of various tax liabilities including provisional estimates associated with the U.S. enacted Tax Cuts and Jobs Act (the 2017 Tax Act), accrual of loss contingencies and calculation of share-based compensation expense. Actual results could be materially different from the estimated provisions and accruals recorded.
New Accounting Pronouncements, Policy		Leases In February 2016, the Financial Accounting Standards Board (FASB) issued an Accounting Standard Update (ASU) changing the accounting for leases and includes a requirement to record all leases exceeding one year on the consolidated balance sheet as assets and liabilities. The Company expects to adopt the standard using a modified retrospective method and initially apply the standard beginning January 1, 2019. Adoption will impact the consolidated balance sheets as future minimum lease payments under noncancelable operating leases totaled approximately $250 million as of June 30, 2018. The Company is currently evaluating its existing lease portfolio, including accumulating all of the necessary information required to make appropriate accounting policy elections and properly account for the leases under this new standard. Additionally, the Company has begun the implementation of an enterprise-wide lease management system that, along with accompanying process changes, will assist in the accounting and internal control changes necessary to meet the reporting and disclosure requirements of the new standard when it becomes effective. Taxes In February 2018, the FASB issued an ASU, which amends existing guidance for reporting comprehensive income to reflect changes resulting from the 2017 Tax Act. The amendment provides the option to reclassify stranded tax effects resulting from the 2017 Tax Act within accumulated other comprehensive income (AOCI) to retained earnings. New disclosures will be required upon adoption, including the accounting policy for releasing income tax effects from AOCI, whether reclassification of stranded income tax effects is elected, and information about other income tax effect reclassifications. The amendment will become effective for the Company on January 1, 2019, though early adoption is permitted. The Company is currently evaluating the impact of adopting this standard on its consolidated financial statements and disclosures.
Stock Plans, Policy		The Company recognizes stock compensation expense based on an estimate of the fair value of awards granted to employees and directors under the Company’s omnibus incentive, stock option, director restricted stock and employee stock purchase rights plans. This expense, adjusted for expected forfeitures, is recognized in net earnings on a straight-line basis over the service periods as salaries and related costs.
Income Taxes, Policy		The 2017 Tax Act included provisions for Global Intangible Low-Taxed Income (GILTI) under which taxes on foreign income are imposed on the excess of a deemed return on tangible assets of certain foreign subsidiaries and for Base Erosion and Anti-Abuse Tax (BEAT) under which taxes are imposed on certain base eroding payments to affiliated foreign companies. Consistent with U.S. GAAP, the Company will treat BEAT as discrete adjustments to the income tax provision when incurred in future periods for which no deferred taxes are required to be provided and has made an accounting policy election to treat GILTI taxes in a similar manner. No provision for income taxes related to GILTI has been recorded through June 30, 2018. In 2017 and during the first quarter of 2018 no provision for BEAT was recorded. However, during the second quarter of 2018 estimated BEAT income tax expense of $2.0 million was recognized. The components of the provisional net income tax benefit recorded in 2017 and through the six-month period ended June 30, 2018 are based on the then currently best available information. Additional information needs to be prepared, obtained and/or analyzed to determine the final amounts. The provisional tax expense for the mandatory repatriation of undistributed international earnings will require further analysis of certain foreign exchange gains or losses, substantiation of foreign tax credits, as well as estimated cash and cash equivalents of the Company's foreign subsidiaries. The provisional tax benefit for the remeasurement of deferred taxes will require additional information necessary for the preparation of the Company's U.S. federal tax return, and further analysis and interpretation of certain provisions of the 2017 Tax Act impacting deferred taxes, for example 100% expensing of qualified assets, could impact the Company's recorded deferred tax balances. The tax effects for these items will be recorded in subsequent quarters of 2018, as discrete adjustments to the income tax provision, once complete. The Company elected to adopt the Securities and Exchange Commission issued guidance that allows for a measurement period, not to exceed one year after the enactment date of the 2017 Tax Act, to finalize the recording of the related tax impacts. The Company will finalize its tax positions and calculations when it files its 2017 U.S. tax returns. At that point, the Company will conclude finally whether any further adjustments are required to its net current and deferred tax accounts in the U.S. as of December 31, 2017, as well as to the provisional liability associated with the Transition Tax. As of June 30, 2018, the Company reclassified its provisional liability associated with the Transition Tax from a long-term liability to a current obligation, offsetting its prepaid income tax balance, as a result of guidance issued by the IRS during the second quarter.
Earnings Per Share, Policy		Diluted earnings attributable to shareholders per share is computed using the weighted average number of common shares and dilutive potential common shares outstanding. Dilutive potential shares represent outstanding stock options, including purchase options under the Company's employee stock purchase plan and unvested restricted stock units. Basic earnings attributable to shareholders per share is calculated using the weighted average number of common shares outstanding without taking into consideration dilutive potential common shares outstanding.
Cash Equivalents, Policy		All highly liquid investments with a maturity of three months or less at date of purchase are considered to be cash equivalents.
Segment Reporting, Policy		The Company is organized functionally in geographic operating segments. Accordingly, management focuses its attention on revenues, net revenues¹, operating income, identifiable assets, capital expenditures, depreciation and amortization and equity generated in each of these geographical areas when evaluating the effectiveness of geographic management. Transactions among the Company’s various offices are conducted using the same arms-length pricing methodologies the Company uses when its offices transact business with independent agents. Certain costs are allocated among the segments based on the relative value of the underlying services, which can include allocation based on actual costs incurred or estimated cost plus a profit margin.