CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net income	$ 55,588	$ 84,886	$ 105,933
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	50,860	47,472	44,893
Provision for doubtful accounts	546	354	19
Deferred income taxes	24,389	10,121	11,212
Excess tax benefits from stock based compensation	(372)	(134)	(1,384)
Lower of cost or market inventory adjustment	5,363
Loss (gain) on disposal or impairment of assets	15,079	(43)	518
Foreign currency transaction loss, net	303	17	76
Stock compensation expense	7,529	5,837	5,335
Changes in operating assets and liabilities:
Trade accounts and other receivables	(9,511)	(22,024)	8,945
Inventories	(25,624)	6,068	(7,589)
Prepaid expenses and other current assets	(112)	(1,136)	(150)
Long-term prepaid expenses	(122)	2,969	12,005
Accounts payable	2,079	4,330	(18,201)
Accrued expenses	(2,487)	1,677	(10,628)
Accrued income taxes, net	(17,726)	(2,823)	5,397
Net cash provided by operating activities	105,782	137,571	156,381
Investing activities
Capital expenditures	(161,469)	(99,936)	(77,189)
Net cash used in investing activities	(161,469)	(99,936)	(77,189)
Financing activities
Proceeds from bank borrowings	25,000		10,000
Repayments on bank borrowings			(10,000)
Net proceeds from stock based compensation			54
Dividends paid	(29,121)	(26,350)	(23,563)
Purchase of common stock	(6,979)	(6,958)	(7,927)
Excess tax benefits from stock based compensation	372	134	1,384
Net cash used in financing activities	(10,728)	(33,174)	(30,052)
Effect of exchange rate changes on cash	(3,537)	(846)	225
Net (decrease) increase in cash and cash equivalents	(69,952)	3,615	49,365
Cash and cash equivalents at beginning of year	94,250	90,635	41,270
Cash and cash equivalents at end of year	24,298	94,250	90,635
Supplemental cash flow information
Interest paid	135	10	78
Income taxes paid	$ 30,619	$ 33,015	$ 36,036