Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
OPERATING ACTIVITIES:
Consolidated net income	$ 43,564	$ 103,879
Adjustments to reconcile consolidated net income to net cash provided by operating activities:
Depreciation and amortization	42,212	44,111
Amortization of debt financing costs	2,608	8,152
Impairment of intangible assets	8,079	158
Non-cash stock compensation expense	9,844	6,446
Non-cash interest expense	0	764
Income from Available for sale securities	(3,032)	0
Deferred income taxes, net	(2,341)	(9,724)
Loss on sale of available-for-sale securities	196	45
Other	(288)	(780)
Changes in operating assets and liabilities:
Trade accounts receivable	105,848	(54,296)
Inventories, net	(6,225)	(2,652)
Prepaid expenses and other current assets	3,076	(23,421)
Trade accounts payable	(13,465)	4,778
Accrued expenses and other liabilities	(30,051)	(41,383)
NET CASH PROVIDED BY OPERATING ACTIVITIES	160,025	36,077
INVESTING ACTIVITIES:
Proceeds from disposal of assets	4,811	5,966
Payments for intangible assets	(200)	(3,375)
Purchases of property, plant and equipment	(50,072)	(29,726)
NET CASH USED IN INVESTING ACTIVITIES	(45,461)	(27,135)
FINANCING ACTIVITIES:
Proceeds from the exercise of stock options	6,897	6,176
Debt financing costs	0	(5,128)
Debt payments	0	(200,000)
NET CASH PROVIDED BY(USED IN) FINANCING ACTIVITIES	6,897	(198,952)
Effect of exchange rate changes on cash and cash equivalents	509	38
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	121,970	(189,972)
Cash and cash equivalents at beginning of period	200,772	346,266
CASH AND CASH EQUIVALENTS AT END OF PERIOD	322,742	156,294
SUPPLEMENTAL DISCLOSURES:
Amount paid for interest	22,124	21,860
Amount paid for income taxes, net	43,901	100,801
Additional capital expenditures included in accounts payable	$ 8,806	$ 43,214