Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Statement of Cash Flows [Abstract]
Net income	$ 67,888	$ 63,531	$ 50,971
Adjustments to reconcile net income to net cash provided by operating activities:
Loss (gain) on sale of assets	(389)	(325)	2,038
Depreciation and amortization	26,821	27,918	27,518
Write-off of software development project	3,140	0	0
Impairment of long-lived assets	0	0	1,025
Impairment of goodwill	0	530	0
Gain on contingent consideration adjustment	(245)	(545)	0
Deferred income taxes	2,537	2,181	3,620
Noncash compensation related to stock plans	11,958	13,190	12,747
Excess tax benefit of options exercised	(78)	(79)	(80)
Provision for (recovery of) doubtful accounts	440	151	(48)
Changes in operating assets and liabilities, net of effects of acquisitions and dispositions:
Trade accounts receivable	(16,818)	(4,568)	(6,651)
Inventories	17,208	(22,428)	8,458
Other current assets	6,274	(3,683)	27
Other noncurrent assets	(1,301)	(600)	237
Trade accounts payable	(1,035)	(11,266)	(2,708)
Accrued liabilities	(5,148)	2,270	2,653
Accrued profit sharing trust contributions	417	(382)	617
Accrued cash profit sharing and commissions	2,530	81	2,611
Other long-term liabilities	(2,930)	2,607	(1,024)
Accrued workers’ compensation	492	(490)	(100)
Income taxes payable	2,446	(872)	4,595
Net cash provided by operating activities	114,207	67,221	106,506
Cash flows from investing activities
Capital expenditures	(34,186)	(23,715)	(16,804)
Business acquisitions, net of cash acquired	(4,179)	(220)	(6,493)
Loan made to customer	0	(281)	0
Loan repayment by customer	244	39	0
Loan repayments by related parties	0	0	700
Proceeds from sale of assets and businesses	293	672	5,262
Net cash used in investing activities	(37,828)	(23,505)	(17,335)
Cash flows from financing activities
Repayment of line of credit and other borrowings	(17)	(77)	(81)
Contingent consideration of asset acquisitions	(1,177)	(1,293)	(520)
Repurchase of common stock	(47,144)	(2,981)	(9,825)
Issuance of Company’s common stock	9,720	4,582	15,057
Issuance of Company’s common stock	78	79	80
Dividends paid	(29,352)	(25,918)	(18,130)
Net cash used in financing activities	(67,892)	(25,608)	(13,419)
Effect of exchange rate changes on cash	(9,969)	(9,009)	(97)
Net increase (decrease) in cash and cash equivalents	(1,482)	9,099	75,655
Cash and cash equivalents at beginning of year	260,307	251,208
Cash and cash equivalents at end of year	258,825	260,307	251,208
Cash paid during the year for
Interest	249	117	30
Income taxes	34,008	34,977	23,624
Noncash activity during the year for
Capital expenditures	1,214	1,031	1,082
Asset acquisition	0	0	806
Stock-based compensation	552	402	318
Dividends declared but not paid	7,716	6,843	6,095
Contribution in excess of pension benefit cost	$ 0	$ 39	$ 55