Goodwill and Identifiable Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Goodwill and Identifiable Intangible Assets
Impairment of goodwill and identifiable intangible assets not subject to amortization	$ 0	$ 0
Goodwill
Balance at the beginning of the period	483,591us-gaap_Goodwill	470,506us-gaap_Goodwill
Acquisition of business	180,683us-gaap_GoodwillAcquiredDuringPeriod	16,077us-gaap_GoodwillAcquiredDuringPeriod
Adjustment of purchase price allocations	411	(2,006)
Foreign currency translation of non-USD functional currency subsidiary goodwill	(8,607)us-gaap_GoodwillTranslationAdjustments	(986)us-gaap_GoodwillTranslationAdjustments
Balance at the end of the period	656,078us-gaap_Goodwill	483,591us-gaap_Goodwill
Aviation Segment
Goodwill
Balance at the beginning of the period	115,507	109,332
Acquisition of business	62,770
Adjustment of purchase price allocations		6,500
Foreign currency translation of non-USD functional currency subsidiary goodwill	(134)	(325)
Balance at the end of the period	178,143	115,507
Marine segment
Goodwill
Balance at the beginning of the period	69,088	69,931
Acquisition of business	4,660
Foreign currency translation of non-USD functional currency subsidiary goodwill	(680)	(843)
Balance at the end of the period	73,068	69,088
Land Segment
Goodwill
Balance at the beginning of the period	298,996	291,243
Acquisition of business	113,253	16,077
Adjustment of purchase price allocations	411	(8,506)
Foreign currency translation of non-USD functional currency subsidiary goodwill	(7,793)	182
Balance at the end of the period	$ 404,867	$ 298,996

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Total loss recognized during the period from the impairment of goodwill plus the loss recognized in the period resulting from the impairment of the carrying amount of intangible assets, other than goodwill.

+ References

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e961-128460

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Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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