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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.

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Acquisitions Acquisitions (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 24, 2014	Jun. 23, 2014
Business Acquisition [Line Items]
Goodwill	$ 58,326us-gaap_Goodwill	$ 62,021us-gaap_Goodwill	$ 9,884us-gaap_Goodwill	$ 9,453us-gaap_Goodwill
Crude [Member]
Business Acquisition [Line Items]
Goodwill	36,116	28,322
Crude [Member] \| Chesapeake crude oil trucking assets [Member]
Business Acquisition [Line Items]
Property, plant, and equipment acquired						19,092
Customer contract intangible asset acquired					17,000	17,010
Goodwill						7,892
Total assets acquired						$ 43,994