Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES:
Consolidated net income	$ 41,027	$ 41,886
Adjustments to reconcile consolidated net income to net cash provided by operating activities:
Depreciation and amortization	20,914	22,468
Amortization of debt financing costs	1,304	6,311
Impairment of intangible assets	225	158
Non-cash stock compensation expense	4,709	2,921
Non-cash interest expense	0	454
Deferred income taxes, net	(1,174)	(8,009)
Other	31	0
Changes in operating assets and liabilities:
Trade accounts receivable	49,563	(21,355)
Inventories, net	2,708	(5,928)
Prepaid expenses and other current assets	4,137	(1,190)
Trade accounts payable	(4,286)	(1,948)
Accrued expenses and other liabilities	8,296	(26,783)
NET CASH PROVIDED BY OPERATING ACTIVITIES	127,454	8,985
INVESTING ACTIVITIES:
Proceeds from disposal of assets	152	0
Payments for intangible assets	0	(1,000)
Purchases of property, plant and equipment	(22,483)	(9,918)
NET CASH USED IN INVESTING ACTIVITIES	(22,331)	(10,918)
FINANCING ACTIVITIES:
Proceeds from the exercise of stock options	1,115	0
Debt financing costs	0	(3,571)
Debt payments	0	(200,000)
NET CASH PROVIDED BY(USED IN) FINANCING ACTIVITIES	1,115	(203,571)
Effect of exchange rate changes on cash and cash equivalents	415	236
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	106,653	(205,268)
Cash and cash equivalents at beginning of period	200,772	346,266
CASH AND CASH EQUIVALENTS AT END OF PERIOD	307,425	140,998
SUPPLEMENTAL DISCLOSURES:
Amount paid for interest	11,041	10,613
Amount (received) paid for income taxes, net	(42)	43,075
Additional capital expenditures included in accounts payable	$ 7,571	$ 2,874