Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 33,039	$ 30,097
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	21,836	15,808
Stock-based compensation expense	4,289	3,003
Provision for deferred income taxes	(278)	178
Net provision for doubtful accounts	220	1,073
(Gain) loss on sale of assets	(323)	104
Increase in receivables	(18,442)	(10,793)
Decrease (increase) in inventories	4,055	(870)
Increase in other assets	(199)	(2,826)
Decrease in accounts payable	(1,237)	(8,705)
Increase (decrease) in accrued liabilities and other	935	(11,247)
Net cash provided by operating activities	43,895	15,822
Cash flows from investing activities:
Capital expenditures	(37,417)	(26,315)
Proceeds from sale of property, plant and equipment	590	371
Net cash used in investing activities	(36,827)	(25,944)
Cash flows from financing activities:
Borrowings on lines of credit	159,612	173,846
Payments on lines of credit	(158,679)	(126,233)
Proceeds from employee stock plans	6,928	468
Post-closing payment for business acquisition		(11,892)
Purchase of treasury stock	(2,010)	(24,825)
Other financing activities	(39)	(53)
Net cash provided by financing activities	5,812	11,311
Effect of exchange rate changes on cash	(1,681)	2,396
Net increase in cash and cash equivalents	11,199	3,585
Cash and cash equivalents at beginning of year	46,846	25,247
Cash and cash equivalents at end of period	58,045	28,832
Cash paid for:
Income taxes (net of refunds)	14,471	5,836
Interest	$ 4,485	$ 4,106