CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Series A Nonconvertible Preferred Stock [Member] Preferred Stock [Member]
BALANCE at Dec. 31, 2011	$ 342,227,000	$ 461,000	$ 561,492,000	$ (213,871,000)	$ (5,857,000)	$ 0	$ 2,000
BALANCE (in shares) at Dec. 31, 2011		46,113,296				0	200,000
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Net income	9,660,000			9,660,000
Other comprehensive income	155,000				155,000
Repurchase of common stock (in shares)						205,902
Repurchase of common stock	(5,202,000)					(5,202,000)
Exercise of common stock options and warrants, net of tendered shares (in shares)		222,549
Exercise of common stock options, net of tendered shares	855,000	2,000	853,000
Stock Issued During Period, Shares Share Based Compensation, Net of Shares withheld for employee taxes		170,584
Stock Issued During Period, Value Share Based Compensation, Net of Shares witthheld for employee taxes	1,125,000	2,000	1,123,000
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		43,341
Issuance of common stock to Board of Directors and Scientific Advisory Board	1,094,000	0	1,094,000
Issuance of common stock to employees under an Employee Stock Purchase Plan (ESPP) (in shares)		11,667
Issuance of common stock to employees under an ESPP	321,000	0	321,000
BALANCE at Dec. 31, 2012	350,235,000	465,000	564,883,000	(204,211,000)	(5,702,000)	(5,202,000)	2,000
BALANCE (in shares) at Dec. 31, 2012		46,561,437				205,902	200,000
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Net income	74,052,000			74,052,000
Other comprehensive income	1,334,000				1,334,000
Repurchase of common stock (in shares)						195,599
Repurchase of common stock	(5,456,000)					(5,456,000)
Exercise of common stock options and warrants, net of tendered shares (in shares)		223,714
Exercise of common stock options, net of tendered shares	2,558,000	2,000	2,556,000
Stock Issued During Period, Shares Share Based Compensation, Net of Shares withheld for employee taxes		(13,502)
Stock Issued During Period, Value Share Based Compensation, Net of Shares witthheld for employee taxes	3,519,000	0	3,519,000
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		39,153
Issuance of common stock to Board of Directors and Scientific Advisory Board	1,101,000	1,000	1,100,000
Issuance of common stock to employees under an Employee Stock Purchase Plan (ESPP) (in shares)		14,366
Issuance of common stock to employees under an ESPP	343,000	0	343,000
BALANCE at Dec. 31, 2013	427,686,000	468,000	572,401,000	(130,159,000)	(4,368,000)	(10,658,000)	2,000
BALANCE (in shares) at Dec. 31, 2013		46,825,168				401,501	200,000
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Net income	41,854,000
Other comprehensive income	(14,000)				(14,000)
Repurchase of common stock (in shares)						956,362
Repurchase of common stock	(29,500,000)					(29,500,000)
Exercise of common stock options and warrants, net of tendered shares (in shares)		184,798
Exercise of common stock options, net of tendered shares	1,887,000	3,000	1,884,000
Issuance of common stock to employees (shares)		83,834
Issuance of common stock to employees, net of shares withheld for employee taxes	8,027,000	1,000	8,026,000
Shares withheld for employee taxes (shares)		83,831
Shares withheld for employee taxes	(2,844,000)	(1,000)	(2,843,000)
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		39,484
Issuance of common stock to Board of Directors and Scientific Advisory Board	1,318,000	0	1,318,000
Issuance of common stock to employees under an Employee Stock Purchase Plan (ESPP) (in shares)		12,373
Issuance of common stock to employees under an ESPP	328,000	0	328,000
BALANCE at Dec. 31, 2014	$ 448,742,000	$ 471,000	$ 581,114,000	$ (88,305,000)	$ (4,382,000)	$ (40,158,000)	$ 2,000
BALANCE (in shares) at Dec. 31, 2014		47,061,826				1,357,863	200,000