Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash Flows From Operating Activities:
Net Income	$ 26,582	$ 23,629	$ 26,038
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,592	7,610	6,544
Deferred income taxes	(923)	1,462	2,584
Stock-based compensation	1,586	1,482	1,047
Net change in accrued interest, premiums, and discounts on investments	556	817	824
Other	30
Net Cash Provided By Used In Operating Activities Before Changes In Operating Capital, Total	36,423	35,000	37,037
Changes in operating assets and liabilities:
Accounts receivable	(1,110)	(1,831)	298
Inventories	(2,487)	803	(7,182)
Prepaid expenses and other current assets	1,507	(797)	(1,263)
Other non-current assets	(17)	(77)	18
Accounts payable and accrued liabilities	1,768	(2,465)	2,008
Accrued income and other taxes	388	(370)	283
Other non-current liabilities	104	(894)	341
Net Cash Provided by (Used in) Operating Activities, Total	36,576	29,369	31,540
Cash Flows From Investing Activities:
Property, plant and equipment additions	(7,503)	(10,347)	(11,999)
Purchase of patents	(2,150)
Purchase of investments		(26,566)	(14,723)
Proceeds from maturities of investments	7,639	19,750	14,290
Net Cash Provided by (Used in) Investing Activities, Total	(2,014)	(17,163)	(12,432)
Cash Flows From Financing Activities:
Exercise of stock options		731
Shares tendered for employees' withholding taxes on stock-based compensation		(1,136)	(78)
Tax benefit related to stock-based compensation	15	1,412	79
Purchase of treasury stock	(9,196)	(5,344)	(1,513)
Dividends paid	(4,821)	(24,460)	(3,676)
Net Cash Provided by (Used in) Financing Activities, Total	(14,002)	(28,797)	(5,188)
Net change in cash and cash equivalents	20,560	(16,591)	13,920
Cash and cash equivalents, beginning of year	7,999	24,590	10,670
Cash and cash equivalents, end of year	28,559	7,999	24,590
Cash paid for:
Income taxes	$ 8,036	$ 10,357	$ 11,921