Balance Sheet Details (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts receivable:
Accounts receivable	$ 83,385	$ 85,113
Allowance for doubtful accounts	7,464	7,832
Inventories:
Finished goods	156,415	152,261
Work in process	2,006	1,625
Raw materials	4,419	4,432
Repair parts	10,359	10,558
Operating supplies	1,206	1,133
Total inventories, less loss provisions of $9,786 and $9,484	174,405	170,009
Inventory loss provisions	9,786	9,484
Accrued liabilities:
Accrued incentives	18,429	19,771
Other accrued liabilities	22,164	22,036
Total accrued liabilities	40,593	41,807
Trade receivables
Accounts receivable:
Accounts receivable	81,379	82,851
Other receivables
Accounts receivable:
Accounts receivable	$ 2,006	$ 2,262