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Inventories and natural gas in storage (Details 2) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Aggregates held for resale	$ 101,568,000	$ 87,715,000
Materials and supplies	69,808,000	69,390,000
Asphalt oil	38,099,000	67,480,000
Merchandise for resale	21,720,000	31,172,000
Natural gas in storage (current)	16,417,000	29,030,000
Other	34,779,000	32,628,000
Total	282,391,000	317,415,000
Natural gas in storage noncurrent	$ 48,300,000	$ 49,700,000

X

- Definition

Aggregated amount of aggregates held for resale. This amount is net of valuation reserves and adjustments.

+ References

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- Definition

Aggregated amount of asphalt oil inventory. This amount is net of valuation reserves and adjustments.

+ References

No definition available.

+ Details

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- Definition

Carrying amount as of the balance sheet date of natural gas in storage, which largely represents the cost of gas required to maintain pressure levels for normal operating purposes, and deemed to be noncurrent asset.

+ References

No definition available.

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- Definition

Carrying amount as of the balance sheet date of natural gas in storage, which is a mixture of gases (liquefied or otherwise), used for fuel and manufacturing purposes, which is ready for sale.

+ 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))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Subparagraph a

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- Definition

Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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-Publisher SEC

-Name Regulation S-X (SX)

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-Subparagraph (SX 210.5-02.6(a)(1))

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- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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- Definition

Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.

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-Name Regulation S-X (SX)

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Carrying amount, net of valuation reserves and allowances, as of the balance sheet date of inventories not otherwise specified in the taxonomy.

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