Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Class C Special Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2013	$ 40,962	$ 1	$ 0	$ 89,501	$ (68)	$ (48,472)
Balance (in shares) at Dec. 31, 2013		9,629			9
Stock-based Compensation Expense	3,423	$ 0	0	3,423	$ 0	0
Issuance of Common Stock in Equity Offering	46,680	$ 0	0	46,680	$ 0	0
Issuance of Common Stock in Equity Offering (in shares)		1,613			0
Allocation of proceeds from sale of Convertible Notes to Embedded Conversion Option	20,195	$ 0	0	20,195	$ 0	0
Cost of Bond-hedge, Net of Proceeds from Sale of Warrant	(2,575)	0	0	(2,575)	0	0
Issuance of Common Stock upon Warrant Exercise	750	$ 0	0	750	$ 0	0
Issuance of Common Stock upon Warrant Exercise (in shares)		83			0
Issuance of Common Shares upon Stock Option Exercise	819	$ 0	0	819	$ 0	0
Issuance of Common Shares upon Stock Option Exercise (in Shares)		43			0
Issuance of Restricted Stock Awards	0	$ 0	0	(68)	$ 68	0
Issuance of Restricted Stock Awards (in Shares)		20			(9)
Excess Tax Benefit from Stock-based Compensation Awards	784	$ 0	0	784	$ 0	0
Net Income	28,747	0	0	0	0	28,747
Balance at Dec. 31, 2014	139,785	$ 1	0	159,509	$ 0	(19,725)
Balance (in shares) at Dec. 31, 2014		11,388			0
Stock-based Compensation Expense	3,856	$ 0	0	3,856	$ 0	0
Issuance of Common Shares upon Stock Option Exercise	819	$ 0	0	706	$ 113	0
Issuance of Common Shares upon Stock Option Exercise (in Shares)		84			(5)
Changes in Treasury Stock Related to Stock-based Compensation Arrangements	(113)	$ 0	0	0	$ (113)	0
Changes in Treasury Stock Related to Stock-based Compensation Arrangements (in shares)		0			7
Issuance of Restricted Stock Awards	0	$ 0	0	0	$ 0	0
Issuance of Restricted Stock Awards (in Shares)		26			(2)
Excess Tax Benefit from Stock-based Compensation Awards	360	$ 0	0	360	$ 0	0
Net Income	15,375	0	0	0	0	15,375
Balance at Dec. 31, 2015	160,082	$ 1	0	164,431	$ 0	(4,350)
Balance (in shares) at Dec. 31, 2015		11,498			0
Stock-based Compensation Expense	6,067	$ 0	0	6,067	$ 0	0
Changes in Treasury Stock Related to Stock-based Compensation Arrangements	(122)	$ 0	0	0	$ (122)	0
Changes in Treasury Stock Related to Stock-based Compensation Arrangements (in shares)		0			10
Issuance of Common Shares upon Stock Option and ESPP Exercise	1,570	$ 0	0	1,448	$ 122	0
Issuance of Common Shares upon Stock Option and ESPP Exercise (in shares)		119			(10)
Repurchase of Common Stock under Stock Repurchase Program	(2,500)	$ 0	0	0	$ 0	(2,500)
Repurchase of Common Stock under Stock Repurchase Program (in shares)		(65)			0
Issuance of Restricted Stock Awards	0	$ 0	0	0	$ 0	0
Issuance of Restricted Stock Awards (in Shares)		37			0
Excess Tax Benefit from Stock-based Compensation Awards	617	$ 0	0	617	$ 0	0
Net Income	3,934	0	0	0	0	3,934
Balance at Dec. 31, 2016	$ 169,648	$ 1	$ 0	$ 172,563	$ 0	$ (2,916)
Balance (in shares) at Dec. 31, 2016		11,589			0