Inventories and natural gas in storage (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Inventory Disclosure [Abstract]
Aggregates held for resale	$ 183,693	$ 175,782	$ 168,132
Asphalt oil	32,964	28,238	27,587
Natural gas in storage (current)	28,683	21,919	27,135
Materials and supplies	27,253	25,142	26,609
Merchandise for resale	26,639	21,087	21,525
Other	13,053	18,999	15,235
Total	312,285	291,167	286,223
Natural gas in storage noncurrent	$ 47,500	$ 47,500	$ 48,300

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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