Balance Sheet Details (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accounts receivable:
Accounts receivable	$ 98,547	$ 94,379
Allowance for doubtful accounts	6,407	7,066
Inventories:
Finished goods	173,357	159,998
Work in process	1,581	1,183
Raw materials	4,585	4,944
Repair parts	10,790	10,763
Operating supplies	1,166	1,139
Total inventories, less loss provisions of $12,860 and $5,313	191,479	178,027
Inventory loss provisions	12,860	5,313
Accrued liabilities:
Accrued incentives	31,470	21,450
Other accrued liabilities	22,494	23,729
Total accrued liabilities	53,964	45,179
Trade receivables
Accounts receivable:
Accounts receivable	97,057	91,324
Other receivables
Accounts receivable:
Accounts receivable	$ 1,490	$ 3,055