CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Operating activities:
Net income	$ 6,393	$ 5,635
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	576	620
Gain on sale of property and equipment	(10)
Stock-based compensation expense	1,455	735
Recognition of gain on sale of products	(700)	(700)
Changes in operating assets and liabilities:
Income tax receivable	40	11
Prepaid expenses and other assets	(166)	(255)
Restricted cash	2,134	126
Accounts payable and other liabilities	10	(1,170)
Deferred revenue	(254)	(255)
Net cash provided by operating activities	9,478	4,747
Investing activities:
Purchases of marketable securities	(39,881)	(71,243)
Sales and maturities of marketable securities	34,514	74,875
Proceeds from sale of products	700	700
Purchases of property and equipment	(528)	(372)
Proceeds from sale of property and equipment	37	0
Net cash provided by (used in) investing activities	(5,158)	3,960
Financing activities:
Proceeds from issuances of common stock	154	225
Net cash provided by financing activities	154	225
Net increase in cash and cash equivalents	4,474	8,932
Cash and cash equivalents at beginning of period	25,554	7,682
Cash and cash equivalents at end of period	30,028	16,614
Supplemental Disclosure of Cash Flow Information:
Income taxes paid in cash during the period	$ 39