CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 14,678,000	$ 41,854,000	$ 74,052,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred revenue	(8,994,000)	(4,274,000)	(5,880,000)
Depreciation	3,086,000	2,077,000	2,044,000
Amortization of intangibles	10,999,000	10,996,869	10,973,141
Inventory Write-down	33,000,000	3,900,000	0
Amortization of premium and discount on investments, net	(697,000)	(531,000)	(458,000)
Stock-based compensation to employees	9,173,000	7,278,000	6,077,000
Stock-based compensation to Board of Directors and Scientific Advisory Board	1,291,000	995,000	809,000
Deferred income tax expense (benefit)	7,137,000	9,108,000	(41,418,000)
Retirement plan benefit expense	3,354,000	1,679,000	1,665,000
(Increase) decrease in assets:
Accounts receivable	(2,654,000)	(6,418,000)	(7,000,000)
Inventories	(8,639,000)	(30,414,000)	424,000
Other current assets	1,969,000	2,267,000	(2,706,000)
Other assets	251,000	(183,000)	35,000
Increase (decrease) in liabilities:
Accounts payable and accrued expenses	790,000	3,055,000	3,614,000
Other current liabilities	56,000	87,000	(11,000)
Deferred revenue	48,812,000	5,793,000	2,767,000
Net cash provided by operating activities	113,612,000	47,270,000	44,987,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(5,103,000)	(6,153,000)	(4,710,000)
Additions to intangibles	0	0	(359,000)
Purchases of investments	(691,876,000)	(408,974,000)	(362,838,000)
Proceeds from sale of investments	638,411,000	372,818,000	313,132,000
Net cash used in investing activities	(58,568,000)	(42,309,000)	(54,775,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from issuance of common stock	354,000	328,000	343,000
Repurchase of common stock	0	(29,500,000)	(5,456,000)
Proceeds from the exercise of common stock options	2,034,000	1,887,000	2,832,000
Payment of withholding taxes related to stock-based compensation to employees	(5,337,000)	(2,844,000)	(3,268,000)
Net cash used in financing activities	(2,949,000)	(30,129,000)	(5,549,000)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	52,095,000	(25,168,000)	(15,337,000)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	45,418,000	70,586,000	85,923,000
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 97,513,000	$ 45,418,000	$ 70,586,000