CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net (loss) income	$ (109,544)	$ 55,588	$ 84,886
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	54,457	50,860	47,472
Provision for doubtful accounts	1,857	546	354
Deferred income taxes	(56,800)	24,389	10,121
Excess tax benefits from stock based compensation		(372)	(134)
Lower of cost or market adjustment	4,546	5,363
Loss (gain) on disposal or impairment of assets	44,111	15,079	(43)
Foreign currency transaction (gain) loss, net	(94)	303	17
Stock compensation expense	7,547	7,529	5,837
Loss on derivative instruments	11,155
Changes in operating assets and liabilities:
Trade accounts and other receivables	81,371	(9,511)	(22,024)
Inventories	27,022	(25,624)	6,068
Prepaid expenses and other current assets	1,437	(112)	(1,136)
Long-term other assets	697	(122)	2,969
Accounts payable	(7,861)	2,079	4,330
Accrued expenses	(9,104)	(2,487)	1,677
Accrued income taxes, net	19,780	(17,726)	(2,823)
Net cash provided by operating activities	70,577	105,782	137,571
Investing activities
Capital expenditures	(62,747)	(161,469)	(99,936)
Net cash used in investing activities	(62,747)	(161,469)	(99,936)
Financing activities
Proceeds from bank borrowings	70,000	25,000
Repayments on bank borrowings	(7,000)
Dividends paid	(14,666)	(29,121)	(26,350)
Purchase of common stock	(580)	(6,979)	(6,958)
Excess tax benefits from stock based compensation		372	134
Net cash provided by (used in) financing activities	47,754	(10,728)	(33,174)
Effect of exchange rate changes on cash	(1,016)	(3,537)	(846)
Net increase (decrease) in cash and cash equivalents	54,568	(69,952)	3,615
Cash and cash equivalents at beginning of year	24,298	94,250	90,635
Cash and cash equivalents at end of year	78,866	24,298	94,250
Supplemental cash flow information
Interest paid	$ 2,613	135	10
Income taxes paid		$ 30,619	$ 33,015