Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating activities
Net income	$ 92,877	$ 93,942
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	15,139	15,126
Stock-based compensation expense	6,482	5,660
Loss (gain) on sale of equipment	75	(149)
Deferred income taxes	(4,935)	(2,507)
Changes in operating assets and liabilities:
Trade receivables, net	70,508	(33,272)
Inventories, net	3,348	(32,708)
Prepaids and other assets	(2,958)	3,194
Excess tax benefits of stock options and awards	(57)	(251)
Accounts payable and accrued expenses	(67,468)	17,637
Net cash provided by operating activities	113,011	66,672
Investing activities
Purchase of property, plant and equipment	(11,204)	(23,218)
Proceeds from sale of equipment	136	470
Net cash used in investing activities	(11,068)	(22,748)
Financing activities
Repurchase of common stock	(19,943)	(90,022)
Proceeds from exercise of stock options	1,952	1,386
Excess tax benefits of stock options and awards	57	251
Net cash used in financing activities	(179,347)	(88,385)
Effect of exchange rate changes on cash activities	(41)	2,726
Increase (decrease) in cash and cash equivalents	83,968	(41,735)
Cash and cash equivalents at beginning of period	298,705	384,356
Cash and cash equivalents at end of period	$ 382,673	$ 342,621