Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 17,375	$ 15,634
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	10,954	8,018
Stock-based compensation expense	1,973	1,383
Provision for deferred income taxes	534	81
Net provision for doubtful accounts	208	414
(Gain) loss on sale of assets	(99)	244
Change in assets and liabilities:
Increase in receivables	(20,969)	(24,439)
Increase in inventories	(1,280)	(12,144)
Increase in other assets	(2,382)	(1,755)
Increase in accounts payable	4,179	9,008
Increase (decrease) in accrued liabilities and other	4,747	(2,852)
Net cash provided by (used in) operating activities	15,240	(6,408)
Cash flows from investing activities:
Capital expenditures	(16,127)	(17,302)
Proceeds from sale of property, plant and equipment	213	8
Net cash used in investing activities	(15,914)	(17,294)
Cash flows from financing activities:
Borrowings on lines of credit	71,102	85,951
Payments on lines of credit	(78,748)	(50,632)
Proceeds from employee stock plans	3,808	234
Purchase of treasury stock		(7,598)
Other financing activities	(38)	10
Net cash (used in) provided by financing activities	(3,876)	27,965
Effect of exchange rate changes on cash	(586)	859
Net (decrease) increase in cash and cash equivalents	(5,136)	5,122
Cash and cash equivalents at beginning of year	46,846	25,247
Cash and cash equivalents at end of period	41,710	30,369
Cash paid for:
Income taxes (net of refunds)	4,294	(4,378)
Interest	$ 331	$ 100