Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 51,799	$ 48,839
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	33,138	24,406
Stock-based compensation expense	6,954	5,027
Provision for deferred income taxes	(311)	(4,654)
Net provision for doubtful accounts	221	1,282
(Gain) loss on sale of assets	(437)	512
Excess tax benefit from stock-based compensation	(2,020)
Change in assets and liabilities:
Decrease in receivables	1,210	11,964
Decrease (increase) in inventories	2,964	(6,446)
Decrease (increase) in other assets	828	(98)
(Decrease) increase in accounts payable	(11,832)	2,905
Increase (decrease) in accrued liabilities and other	13,175	(3,085)
Net cash provided by operating activities	95,689	80,652
Cash flows from investing activities:
Capital expenditures	(52,550)	(34,858)
Proceeds from sale of property, plant and equipment	1,248	823
Net cash used in investing activities	(51,302)	(34,035)
Cash flows from financing activities:
Borrowings on lines of credit	215,994	222,868
Payments on lines of credit	(243,141)	(213,221)
Proceeds from employee stock plans	8,102	1,007
Post-closing payment for business acquisition		(11,892)
Purchase of treasury stock	(4,227)	(35,698)
Excess tax benefit from stock-based compensation	2,020
Other financing activities	(25)	(48)
Net cash used in financing activities	(21,277)	(36,984)
Effect of exchange rate changes on cash	(547)	577
Net increase in cash and cash equivalents	22,563	10,210
Cash and cash equivalents at beginning of year	46,846	25,247
Cash and cash equivalents at end of period	69,409	35,457
Cash paid for:
Income taxes (net of refunds)	21,637	17,370
Interest	$ 5,047	$ 4,665