Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 129,565	$ 267,705	$ 178,653
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	571,961	581,940	555,186
Gain on sale of real estate	0	(108,109)	0
Amortization of deferred debt issuance costs and premiums	1,120	1,235	1,403
Deferred income taxes	(13,110)	(42,189)	1,443
Loss on debt retirement	1,512	4,835	0
Loss (gain) on disposal of fixed assets, net	5,310	(2,648)	1,390
Share-based compensation	5,018	5,145	3,251
Proceeds from insurance recovery for property, plant and equipment	(1,371)	0	(15,166)
Other, net	3,929	(8,143)	2,858
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	80,571	(133,814)	(55,184)
Inventories	(16,310)	(36,307)	(8,623)
Other current assets	4,329	(2,473)	1,124
Other assets	1,986	(458)	1,037
Trade accounts payable	(43,490)	67,574	48,581
Accrued expenses	(78,136)	29,424	48,159
Pension and severance obligations	(4,653)	23,881	1,625
Other non-current liabilities	15,179	(29,331)	(36,335)
Net cash provided by operating activities	663,410	618,267	729,402
Cash flows from investing activities:
Payments for property, plant and equipment	(547,122)	(550,943)	(650,038)
Proceeds from sale of property, plant and equipment	2,841	141,530	45,635
Proceeds from insurance recovery for property, plant and equipment	1,371	0	15,166
Acquisition of business, net of cash acquired	0	(43,771)	0
Other investing activities	5,527	(1,648)	(190)
Net cash used in investing activities	(537,383)	(454,832)	(589,427)
Cash flows from financing activities:
Proceeds from revolving credit facilities	0	75,000	125,000
Payments of revolving credit facilities	(75,000)	0	(255,000)
Proceeds from short-term debt	23,341	77,781	49,131
Payments of short-term debt	(46,631)	(70,236)	(49,500)
Proceeds from issuance of long-term debt	596,226	223,976	46,000
Payments of long-term debt	(535,738)	(405,269)	(32,078)
Payments of long-term debt, related party	0	(17,837)	0
Payments of capital lease obligations	(3,930)	(5,340)	(2,543)
Payment of deferred consideration for purchase of facility	0	(3,890)	0
Proceeds from issuance of stock through share-based compensation plans	1,050	3,124	8,247
Other financing activities	59	(2,195)	(1,436)
Net cash used in financing activities	(40,623)	(124,886)	(112,179)
Effect of exchange rate fluctuations on cash, cash equivalents and restricted cash	(204)	8,807	351
Net increase in cash, cash equivalents and restricted cash	85,200	47,356	28,147
Cash, cash equivalents and restricted cash, beginning of period	602,851	555,495	527,348
Cash, cash equivalents and restricted cash, end of period	688,051	602,851	555,495
Cash paid during the period for:
Interest	77,575	83,808	86,777
Income taxes	63,080	61,878	32,174
Non-cash investing and financing activities:
Property, plant and equipment included in capital expenditures payable	256,070	294,912	146,080
Equipment acquired through capital lease	$ 17,163	$ 929	$ 6,358