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Inventories and natural gas in storage (Details) - USD ($) $ in Thousands | Mar. 31, 2016 | Dec. 31, 2015 | Mar. 31, 2015
--- | --- | --- | ---
Inventory Disclosure [Abstract] |  |  |
Aggregates held for resale | $ 127,101 | $ 115,854 | $ 112,029
Asphalt oil | 52,065 | 36,498 | 89,578
Natural gas in storage (current) | 11,305 | 21,023 | 9,303
Materials and supplies | 21,645 | 16,997 | 57,073
Merchandise for resale | 17,441 | 15,318 | 15,688
Crude oil | 3,034 | 4,678 | 7,076
Refined products | 14,022 | 8,498 | 0
Other | 30,199 | 34,861 | 37,325
Total | 276,812 | 253,727 | 328,072
Natural gas in storage noncurrent | $ 49,100 | $ 49,100 | $ 49,300

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- Definition The aggregate carrying amount as of the balance sheet date of unrefined petroleum and the liquid hydrocarbon components recovered from natural gas. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Carrying amount as of the balance sheet date of natural gas stored underground in depleted gas reservoirs, aquifers, or salt caverns to meet future seasonal and peak load demands and also as insurance against unforeseen supply disruptions, and deemed to be a noncurrent asset because it is not expected to be used within 12 months or in the normal operating cycle. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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