CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 11,476	$ 13,877
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,562	3,163
Deferred income taxes	315	1,395
Stock-based compensation	729	461
Net change in accrued interest, premiums, and discounts on investments	368	361
Net Cash Provided By Used In Operating Activities Before Changes In Operating Capital	16,450	19,257
Changes in operating assets and liabilities:
Accounts receivable	(3,698)	(3,314)
Inventories	(317)	(3,688)
Prepaid expenses	95	(1,730)
Other non-current assets	(81)	18
Accounts payable and accrued liabilities	(1,198)	2,738
Accrued income and other taxes	(369)	255
Other non-current liabilities	13	58
Net Cash Provided by (Used in) Operating Activities, Total	10,895	13,594
Cash flows from investing activities:
Property, plant and equipment additions	(5,580)	(5,519)
Purchase of investments	(21,545)	(9,723)
Proceeds from maturities of investments	6,750	2,400
Net Cash Provided by (Used in) Investing Activities, Total	(20,375)	(12,842)
Cash flows from financing activities:
Shares tendered for employees' taxes on stock-based compensation	(1,065)
Issuance of treasury stock	153
Purchase of treasury stock	(4,756)
Tax benefit related to stock-based compensation	929	19
Dividends paid	(1,976)	(1,697)
Net Cash Provided by (Used in) Financing Activities, Total	(6,715)	(1,678)
Net change in cash and cash equivalents	(16,195)	(926)
Cash and cash equivalents at beginning of period	24,590	10,670
Cash and cash equivalents at end of period	8,395	9,744
Cash paid for:
Income taxes	$ 4,597	$ 6,893