CONSOLIDATED STATEMENTS OF Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 67,319	$ 66,127	$ 62,860
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation	19,627	20,388	20,758
Deferred income taxes	199	255	(946)
Net loss on step acquisition			529
Amortization of marketable security premiums	2,830	3,105	3,261
Changes in operating assets and liabilities:
Accounts receivable	6,869	(8,929)	(2,007)
Other receivables	473	1,119	1,289
Inventories	4,183	7,530	(7,329)
Prepaid expenses and other assets	2,999	11,593	9,524
Accounts payable and accrued liabilities	(2,061)	3,839	(1,268)
Income taxes payable	(5,797)	(115)	(78)
Postretirement health care benefits	(1,216)	(903)	(1,289)
Deferred compensation and other liabilities	3,125	(12,936)	3,465
Net cash provided by operating activities	98,550	91,073	88,769
CASH FLOWS FROM INVESTING ACTIVITIES:
Net cash acquired in step acquisition			161
Change in restricted cash		1,149	224
Capital expenditures	(16,090)	(15,534)	(10,704)
Purchases of trading securities	(4,569)	(4,095)	(4,294)
Sales of trading securities	1,433	16,644	727
Purchase of available for sale securities	(81,835)	(61,951)	(54,882)
Sale and maturity of available for sale securities	49,177	55,264	38,309
Net cash used in investing activities	(51,884)	(8,523)	(30,459)
CASH FLOWS FROM FINANCING ACTIVITIES:
Shares purchased and retired	(29,093)	(33,004)	(25,020)
Dividends paid in cash	(22,266)	(20,775)	(19,241)
Proceeds from bank loans	2,760
Repayment of bank loans	(2,788)	(133)	(403)
Net cash used in financing activities	(51,387)	(53,912)	(44,664)
Effect of exchange rate changes on cash	(2,279)	(2,601)	(1,821)
Increase (decrease) in cash and cash equivalents	(7,000)	26,037	11,825
Cash and cash equivalents at beginning of year	126,145	100,108	88,283
Cash and cash equivalents at end of year	119,145	126,145	100,108
Supplemental cash flow information:
Income taxes paid	36,365	24,940	26,599
Interest paid	34	17	34
Stock dividend issued	$ 61,671	$ 57,220	$ 52,165