Balance Sheet Details (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Accounts receivable:
Accounts receivable	$ 94,370	$ 91,106
Allowance for doubtful accounts	5,986	5,586
Inventories:
Finished goods	165,652	151,698
Work in process	1,214	1,153
Raw materials	4,321	4,708
Repair parts	10,950	10,840
Operating supplies	1,164	1,429
Total inventories, less loss provisions of $4,172 and $4,370	183,301	169,828
Inventory loss provisions	4,172	4,370
Prepaid and other current assets:
Value added tax	15,181	13,512
Prepaid expenses	6,931	6,947
Deferred income taxes	4,883	4,888
Prepaid income taxes	1,943	1,951
Derivative asset	477	403
Total prepaid and other current assets	29,415	27,701
Other assets:
Deposits	1,263	890
Finance fees — net of amortization	6,655	6,958
Other assets	6,597	6,128
Total other assets	14,515	13,976
Accrued liabilities:
Accrued incentives	18,120	17,648
Workers compensation	7,134	7,121
Medical liabilities	3,817	3,887
Interest	3,759	3,876
Commissions payable	1,156	1,068
Withholdings and other non-income tax accruals	3,615	3,078
Other accrued liabilities	5,940	5,960
Total accrued liabilities	43,541	42,638
Other long-term liabilities:
Deferred liability	8,686	8,081
Derivative liability	338	215
Environmental obligation (see note 14)	1,000	1,000
Other long-term liabilities	4,080	3,860
Total other long-term liabilities	14,104	13,156
Trade receivables
Accounts receivable:
Accounts receivable	90,274	87,700
Other receivables [Member]
Accounts receivable:
Accounts receivable	$ 4,096	$ 3,406