Inventories and natural gas in storage (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Inventory Disclosure [Abstract]
Aggregates held for resale	$ 155,976	$ 147,723	$ 142,747
Asphalt oil	73,842	41,912	83,459
Materials and supplies	26,293	22,512	26,441
Merchandise for resale	23,109	22,232	25,104
Natural gas in storage (current)	7,872	22,058	11,464
Other	18,866	21,970	22,320
Total	305,958	278,407	311,535
Natural gas in storage noncurrent	$ 48,300	$ 48,400	$ 48,200

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

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- Definition

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

+ 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

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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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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.

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

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

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