Balance Sheet Details (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable:
Accounts receivable	$ 85,593	$ 89,997
Allowance for doubtful accounts	9,803	9,051
Inventories:
Finished goods	185,957	170,774
Work in process	1,529	1,485
Raw materials	3,876	3,906
Repair parts	10,738	10,240
Operating supplies	1,544	1,481
Total inventories, less loss provisions of $10,691 and $10,308	203,644	187,886
Inventory loss provisions	10,691	10,308
Accrued liabilities:
Accrued incentives	18,689	19,728
Other accrued liabilities	25,166	23,495
Total accrued liabilities	43,855	43,223
Trade receivables
Accounts receivable:
Accounts receivable	84,320	88,786
Other receivables
Accounts receivable:
Accounts receivable	$ 1,273	$ 1,211