Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Cash Flows [Abstract]
Net income	$ 16,343	$ 10,051
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of assets	(26)	(15)
Depreciation and amortization	7,437	7,418
Write-off of software development project	153	0
Gain on contingent consideration adjustment	0	(245)
Deferred income taxes	2,499	2,593
Noncash compensation related to stock plans	2,750	3,295
Excess tax benefit of options exercised and restricted stock units vested	(28)	(58)
Provision for doubtful accounts	(266)	(50)
Changes in operating assets and liabilities, net of acquisitions:
Trade accounts receivable	(28,228)	(27,615)
Inventories	(13,912)	7,515
Trade accounts payable	7,273	(1,590)
Income taxes payable	6,289	1,740
Accrued profit sharing trust contributions	(3,552)	(3,421)
Accrued cash profit sharing and commissions	2,605	1,179
Other current assets	(3,230)	(1,101)
Accrued liabilities	(10,063)	(11,295)
Long-term liabilities	(1,853)	93
Accrued workers’ compensation	(121)	377
Other noncurrent assets	2,162	871
Net cash used in operating activities	(13,768)	(10,258)
Cash flows from investing activities
Capital expenditures	(6,972)	(6,369)
Asset acquisitions, net of cash acquired	0	(779)
Proceeds from sale of property and equipment	40	25
Loan repayment by customer	0	243
Net cash used in investing activities	(6,932)	(6,880)
Cash flows from financing activities
Deferred and contingent consideration paid for asset acquisition	(27)	(1,177)
Repurchase of common stock	(3,502)	0
Repayment of debt and line of credit borrowings	0	(17)
Issuance of common stock	1,012	5,484
Excess tax benefit of options exercised and restricted stock units vested	28	58
Dividends paid	(7,709)	(6,858)
Net cash used in financing activities	(10,198)	(2,510)
Effect of exchange rate changes on cash and cash equivalents	4,101	(7,072)
Net decrease in cash and cash equivalents	(26,797)	(26,720)
Cash and cash equivalents at beginning of period	258,825	260,307
Cash and cash equivalents at end of period	232,028	233,587
Noncash activity during the period
Noncash capital expenditures	266	830
Dividends declared but not paid	7,729	6,927
Issuance of Company’s common stock for compensation	$ 315	$ 552