CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 41,854	$ 74,052	$ 9,660
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred revenue	(4,274)	(5,880)	(5,284)
Depreciation	2,077	2,044	1,978
Amortization of intangibles	10,997	10,973	4,869
Amortization of premium and discount on investments, net	(531)	(458)	(778)
Stock-based compensation to employees	7,278	6,077	4,263
Stock-based compensation to Board of Directors and Scientific Advisory Board	995	809	781
Deferred income tax expense (benefit)	9,108	(41,418)	(11)
Retirement plan benefit expense	1,679	1,665	1,600
(Increase) decrease in assets:
Accounts receivable	(6,418)	(7,000)	2,070
Inventories	(26,514)	424	(7,175)
Other current assets	2,267	(2,706)	(2,284)
Other assets	(183)	35	33
Increase (decrease) in liabilities:
Accounts payable and accrued expenses	3,055	3,614	4,718
Other current liabilities	87	(11)	11
Deferred revenue	5,793	2,767	3,303
Net cash provided by operating activities	47,270	44,987	17,754
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(6,153)	(4,710)	(2,737)
Additions to intangibles	0	(359)	(109,102)
Purchases of investments	(408,974)	(362,838)	(304,500)
Proceeds from sale of investments	372,818	313,132	380,253
Net cash used in investing activities	(42,309)	(54,775)	(36,086)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from issuance of common stock	328	343	321
Repurchase of common stock	(29,500)	(5,456)	(5,202)
Proceeds from the exercise of common stock options and warrants	1,887	2,832	1,483
Payment of withholding taxes related to stock-based employee compensation	(2,844)	(3,268)	(4,142)
Net cash used in financing activities	(30,129)	(5,549)	(7,540)
DECREASE IN CASH AND CASH EQUIVALENTS	(25,168)	(15,337)	(25,872)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	70,586	85,923
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 45,418	$ 70,586	$ 85,923