Supplemental balance sheet and cash flow information (inventories and supplies) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Inventories and supplies
Raw materials	$ 7,675		$ 5,316
Semi-finished goods	7,051		6,708
Finished goods	29,550		21,995
Supplies	6,496		6,041
Reserves for excess and obsolete items	(5,523)	$ (5,496)	(5,132)
Inventories and supplies	45,249		$ 34,928
Changes in reserves for excess and obsolete items
Balance, beginning of year	5,132	11,748
Balance, end of period	5,523	5,496
Reserves for excess and obsolete items
Changes in reserves for excess and obsolete items
Amounts charged to expense	2,552	2,884
Write-offs and other	$ (2,161)	$ (9,136)