CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows From Operating Activities:
Net Income	$ 23,629	$ 26,038	$ 20,952
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,610	6,544	7,041
Deferred income taxes	1,462	2,584	309
Stock-based compensation	1,482	1,047	606
Net change in accrued interest, premiums, and discounts on investments	817	824	(183)
Net Cash Provided By Used In Operating Activities Before Changes In Operating Capital	35,000	37,037	28,725
Changes in operating assets and liabilities:
Accounts receivable	(1,831)	298	(495)
Inventories	803	(7,182)	1,275
Prepaid expenses and other current assets	(797)	(1,263)	(69)
Other non-current assets	(77)	18	(57)
Accounts payable and accrued liabilities	(2,465)	2,008	1,075
Accrued income and other taxes	(370)	283	(5)
Other non-current liabilities	(894)	341	609
Net Cash Provided by (Used in) Operating Activities, Total	29,369	31,540	31,058
Cash Flows From Investing Activities:
Property, plant and equipment additions	(10,347)	(11,999)	(4,293)
Purchase of investments	(26,566)	(14,723)	(19,117)
Proceeds from maturities of investments	19,750	14,290	4,000
Net Cash Provided by (Used in) Investing Activities, Total	(17,163)	(12,432)	(19,410)
Cash Flows From Financing Activities:
Exercise of stock options	731		542
Shares tendered for employees' withholding taxes on stock-based compensation	(1,136)	(78)	(725)
Tax benefit related to stock-based compensation	1,412	79	1,239
Purchase of treasury stock	(5,344)	(1,513)	(1,407)
Dividends paid	(24,460)	(3,676)	(21,321)
Net Cash Provided by (Used in) Financing Activities, Total	(28,797)	(5,188)	(21,672)
Net change in cash and cash equivalents	(16,591)	13,920	(10,024)
Cash and cash equivalents, beginning of year	24,590	10,670	20,694
Cash and cash equivalents, end of year	7,999	24,590	10,670
Cash paid for:
Income taxes	$ 10,357	$ 11,921	$ 9,080