Balance Sheet Details (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Accounts receivable:
Accounts receivable	$ 87,901	$ 94,379
Allowance for doubtful accounts	6,063	7,066
Inventories:
Finished goods	173,597	159,998
Work in process	1,619	1,183
Raw materials	4,497	4,944
Repair parts	11,057	10,763
Operating supplies	1,180	1,139
Total inventories, less loss provisions of $5,533 and $5,313	191,950	178,027
Inventory loss provisions	5,533	5,313
Accrued liabilities:
Accrued incentives	20,865	21,450
Other accrued liabilities	21,680	23,729
Total accrued liabilities	42,545	45,179
Trade receivables
Accounts receivable:
Accounts receivable	84,203	91,324
Other receivables
Accounts receivable:
Accounts receivable	$ 3,698	$ 3,055