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SIGNIFICANT ACCOUNTING POLICIES - Dividends, Advertising and Marketable securities (Details) - USD ($)		12 Months Ended
	Jan. 28, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting policies:
Prepaid expenses related to unamortized product brochure costs		$ 269,000	$ 243,000
Net realized (losses) gains on marketable securities		4,000	(81,000)	$ 30,000
Reclassification of net realized (losses) gains from other comprehensive income		4,000	(81,000)	30,000
Gross unrealized gains on marketable securities		0	3,000
Gross unrealized losses on marketable securities		0	12,000
Unrealized loss on marketable securities totaled			9,000
Selling, general and administrative expenses
Accounting policies:
Advertising expenses		$ 2,543,000	$ 2,468,000	$ 2,305,000
Dividend declared
Accounting policies:
Amount of dividend payable in cash per share	$ 0.12
Dividends payable, date declared	Jan. 28, 2020
Dividend payable, date to be payable	Mar. 10, 2020
Dividends payable, date of record	Feb. 10, 2020