Balance Sheet Details (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accounts receivable:
Accounts receivable	$ 88,969	$ 85,113
Allowance for doubtful accounts	8,561	7,832
Inventories:
Finished goods	162,084	152,261
Work in process	1,791	1,625
Raw materials	4,198	4,432
Repair parts	10,721	10,558
Operating supplies	1,272	1,133
Total inventories, less loss provisions of $10,417 and $9,484	180,066	170,009
Inventory loss provisions	10,417	9,484
Accrued liabilities:
Accrued incentives	25,398	19,771
Other accrued liabilities	24,750	22,036
Total accrued liabilities	50,148	41,807
Trade receivables
Accounts receivable:
Accounts receivable	87,330	82,851
Other receivables
Accounts receivable:
Accounts receivable	$ 1,639	$ 2,262