Segment Information Segments (Details) (USD $)	3 Months Ended
Mar. 31, 2015 reportable_segment region	Mar. 31, 2014
Segment Reporting Information [Line Items]
Number of operating regions	11us-gaap_NumberOfOperatingSegments
Number of reportable segments	2us-gaap_NumberOfReportableSegments
Operating revenues	$ 397,030,000us-gaap_SalesRevenueNet	$ 376,279,000us-gaap_SalesRevenueNet
Income from operations	72,620,000us-gaap_OperatingIncomeLoss	74,875,000us-gaap_OperatingIncomeLoss
Depreciation and amortization	41,813,000	37,641,000
Interest expense	13,508,000us-gaap_InterestExpense	13,641,000us-gaap_InterestExpense
Loss on settlement of foreign currency forward purchase contracts	18,686,000	0
Interest income	26,000us-gaap_InvestmentIncomeInterest	1,034,000us-gaap_InvestmentIncomeInterest
Provision for income taxes	16,862,000us-gaap_IncomeTaxExpenseBenefit	22,900,000us-gaap_IncomeTaxExpenseBenefit
Expenditures for additions to property & equipment, net of grants from outside parties	49,898,000	58,818,000
North American & European Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	322,744,000	299,987,000
Income from operations	56,896,000	55,690,000
Depreciation and amortization	35,651,000	30,579,000
Interest expense	11,017,000	9,445,000
Loss on settlement of foreign currency forward purchase contracts	16,374,000
Interest income	13,000	902,000
Provision for income taxes	13,685,000	18,457,000
Expenditures for additions to property & equipment, net of grants from outside parties	45,283,000	53,985,000
Australian Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues	59,151,000	76,292,000
Income from operations	14,588,000	19,185,000
Depreciation and amortization	6,162,000	7,062,000
Interest expense	2,345,000	4,196,000
Loss on settlement of foreign currency forward purchase contracts	2,312,000
Interest income	8,000	132,000
Provision for income taxes	2,928,000	4,443,000
Expenditures for additions to property & equipment, net of grants from outside parties	4,615,000	4,833,000
Freightliner [Member]
Segment Reporting Information [Line Items]
Operating revenues	15,135,000
Income from operations	1,136,000
Depreciation and amortization	0
Interest expense	146,000
Loss on settlement of foreign currency forward purchase contracts	0
Interest income	5,000
Provision for income taxes	249,000
Expenditures for additions to property & equipment, net of grants from outside parties	$ 0

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Amount of realized and unrealized gain (loss) of foreign currency forward purchase contracts not designated or qualifying as hedging instruments.

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Depreciation of property, plant and equipment directly related to services rendered by an entity during the reporting period.

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-Name Accounting Standards Codification

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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The net result for the period of deducting operating expenses from operating revenues.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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