Balance Sheet Details (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts receivable:
Accounts receivable	$ 81,917	$ 83,977
Allowances for accounts receivable	7,846	8,538
Inventories:
Finished goods	192,625	175,074
Work in process	1,555	1,363
Raw materials	3,886	4,026
Repair parts	10,206	10,116
Operating supplies	1,596	1,524
Total inventories, less loss provisions of $8,398 and $9,453	209,868	192,103
Inventory loss provisions	8,398	9,453
Accrued liabilities:
Accrued incentives	15,924	19,359
Other accrued liabilities	23,213	24,369
Total accrued liabilities	39,137	43,728
Trade receivables
Accounts receivable:
Accounts receivable	80,095	82,521
Other receivables
Accounts receivable:
Accounts receivable	$ 1,822	$ 1,456