CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2011	$ 82,729	$ 409	$ 456,056	$ 10,250	$ (383,986)
Beginning balance, Shares at Dec. 31, 2011		40,928
Net income	(9,040)				(9,040)
Net unrealized change on investments (net of tax of $0)	(1,546)			(1,546)
Forfeitures and repurchases of restricted common stock, Value	(6)		(6)
Forfeitures and repurchases of restricted common stock, Shares		(6)
Stock-based compensation, Value	604		604
Issuance of shares under Employee Stock Purchase Plan, Value	52	1	51
Issuance of shares under Employee Stock Purchase Plan, Shares		40
Ending balance at Dec. 31, 2012	72,793	410	456,705	8,704	(393,026)
Ending balance, Shares at Dec. 31, 2012		40,962
Net income	9,180				9,180
Net unrealized change on investments (net of tax of $0)	(5,329)			(5,329)
Forfeitures and repurchases of restricted common stock, Value	(7)	(1)	(6)
Forfeitures and repurchases of restricted common stock, Shares		(19)
Stock-based compensation, Value	243		243
Stock-based compensation, Shares		5
Issuance of shares under Employee Stock Purchase Plan, Value	52	1	51
Issuance of shares under Employee Stock Purchase Plan, Shares		35
Ending balance at Dec. 31, 2013	76,932	410	456,993	3,375	(383,846)
Ending balance, Shares at Dec. 31, 2013	40,983	40,983
Net income	28,068				28,068
Net unrealized change on investments (net of tax of $0)	1,715			1,715
Forfeitures and repurchases of restricted common stock, Value	(10)		(10)
Forfeitures and repurchases of restricted common stock, Shares		(4)
Stock-based compensation, Value	185		185
Stock-based compensation, Shares		6
Issuance of shares under Employee Stock Purchase Plan, Value	74		74
Issuance of shares under Employee Stock Purchase Plan, Shares		31
Ending balance at Dec. 31, 2014	$ 106,964	$ 410	$ 457,242	$ 5,090	$ (355,778)
Ending balance, Shares at Dec. 31, 2014	41,016	41,016