Changes in Operations Freightliner Pro Forma (Details) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2015 USD ($) $ / shares $ / £	Mar. 25, 2015 $ / £
Foreign currency exchange rate \| $ / £	1.51	1.49
Freightliner [Member]
Operating revenues	$ 553,649
Net income	$ 47,789
Basic earnings per common share \| $ / shares	$ 0.86
Diluted earnings per common share \| $ / shares	$ 0.84
Pro Forma [Member] \| Acquisition-related costs [Member] \| Freightliner [Member]
Net income	$ (9,500)
Net income (loss) before tax	(12,600)
Pro Forma [Member] \| Loss on settlement of foreign currency forward purchase contracts [Member] \| Freightliner [Member]
Net income	(11,600)
Net income (loss) before tax	(18,700)
Freightliner [Member] \| Pro Forma [Member] \| Acquisition-related costs [Member]
Net income	(9,100)
Net income (loss) before tax	$ (12,200)

Business Acquisition, Pro Forma Net Income (Loss) Before Tax

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- Definition

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521

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