Balance Sheet Details (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable:
Accounts receivable	$ 83,977	$ 89,997
Allowance for doubtful accounts	8,538	9,051
Inventories:
Finished goods	175,074	170,774
Work in process	1,363	1,485
Raw materials	4,026	3,906
Repair parts	10,116	10,240
Operating supplies	1,524	1,481
Total inventories, less loss provisions of $9,453 and $10,308	192,103	187,886
Inventory loss provision	9,453	10,308
Accrued liabilities:
Accrued incentives	19,359	19,728
Other accrued liabilities	24,369	24,192
Total accrued liabilities	43,728	43,920
Trade receivables
Accounts receivable:
Accounts receivable	82,521	88,786
Other receivables
Accounts receivable:
Accounts receivable	$ 1,456	$ 1,211