Unaudited Quarterly Financial Information (Statement of Operations) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Restated Quarterly Financial Information [Line Items]
Revenue	$ 44,503		$ 42,713		$ 36,238		$ 35,804		$ 37,376		$ 42,030		$ 38,546		$ 29,224		$ 159,258	$ 147,176	$ 121,882
Cost of revenue			24,571		21,714		20,647		22,366		25,200		24,645		17,895		94,206	90,106	74,995
Gross profit	17,229		18,142		14,524		15,157		15,010		16,830		13,901		11,329		65,052	57,070	46,887
Operating expenses:
Selling, general and administrative			7,342		8,409		9,788		8,459		9,605		9,198		7,956		33,656	35,218	35,646
Research and development			5,084		5,294		5,570		5,380		5,707		5,305		5,964		21,700	22,356	17,736
Total operating expenses			12,426		13,703		15,358		13,839		15,312		14,503		13,920		55,356	57,574	53,382
Income (loss) from operations			5,716		821		(201)		1,171		1,518		(602)		(2,591)		9,696	(504)	(6,495)
Interest expense, net			(56)		(56)		(26)		(21)		(27)		(25)		(36)		(116)	(109)	(188)
Amortization of debt discount and prepaid debt costs			(16)		(15)		(11)		0		0		0		(55)		(57)	(55)	(83)
Gain on embedded derivatives and warrants			0		0		0		0		0		0		1,086		0	1,086	2,341
Income (loss) from operations before income taxes			5,644		750		(238)		1,150		1,491		(627)		(1,596)		9,523	418	(4,425)
Income tax provision			416		719		714		635		922		(427)		726		2,349	1,856	1,631
Net income (loss)	2,867	[1]	5,228	[2]	31	[3]	(952)	[4]	515	[5]	569	[6]	(200)	[7]	(2,322)	[8]	7,174	(1,438)	(6,056)
Net income (loss) per share:
Basic (in dollars per share)			$ 0.18		$ 0.00		$ (0.03)		$ 0.02		$ 0.02		$ (0.01)		$ (0.09)		$ 0.25	$ (0.05)	$ (0.23)
Diluted (in dollars per share)			$ 0.18		$ 0.00		$ (0.03)		$ 0.02		$ 0.02		$ (0.01)		$ (0.09)		$ 0.25	$ (0.05)	$ (0.23)
Weighted average common shares outstanding:
Basic (in shares)			28,736		28,672		28,122		27,851		27,733		27,669		27,285		28,568	27,637	26,234
Diluted (in shares)			28,748		28,780		28,122		28,285		28,161		27,669		27,285		28,709	27,637	26,234
Scenario, Previously Reported [Member]
Restated Quarterly Financial Information [Line Items]
Revenue			43,907		40,856		39,230		42,493		41,096		38,463		35,259			157,311
Cost of revenue			25,534		23,876		23,093		26,345		24,547		22,987		21,375			95,254
Gross profit			18,373		16,980		16,137		16,148		16,549		15,476		13,884			62,057
Operating expenses:
Selling, general and administrative			7,344		8,238		9,286		8,566		9,595		11,798		7,985			37,944
Research and development			5,084		5,294		5,596		5,354		5,707		5,297		5,972			22,330
Total operating expenses			12,428		13,532		14,882		13,920		15,302		17,095		13,957			60,274
Income (loss) from operations			5,945		3,448		1,255		2,228		1,247		(1,619)		(73)			1,783
Interest expense, net			(56)		(56)		(26)		(21)		(27)		(25)		(36)			(109)
Amortization of debt discount and prepaid debt costs			(16)		(15)		(11)		0		0		0		(55)			(55)
Gain on embedded derivatives and warrants			0		0		0		0		0		0		1,086			1,086
Income (loss) from operations before income taxes			5,873		3,377		1,218		2,207		1,220		(1,644)		922			2,705
Income tax provision			470		719		714		635		922		(427)		726			1,856
Net income (loss)			5,403		2,658		504		1,572		298		(1,217)		196			849
Net income (loss) per share:
Basic (in dollars per share)			$ 0.19		$ 0.09		$ 0.02		$ 0.06		$ 0.01		$ (0.04)		$ 0.01			$ 0.03
Diluted (in dollars per share)			$ 0.19		$ 0.09		$ 0.02		$ 0.06		$ 0.01		$ (0.04)		$ 0.01			$ 0.03
Weighted average common shares outstanding:
Basic (in shares)			28,736		28,672		28,122		27,851		27,733		27,669		27,285			27,637
Diluted (in shares)			28,748		28,780		28,559		28,285		28,161		27,669		28,112			28,161
Restatement Adjustment [Member]
Restated Quarterly Financial Information [Line Items]
Revenue			(1,194)		(4,618)		(3,426)		(5,117)		934		83		(6,035)			(10,135)
Cost of revenue			(963)		(2,162)		(2,446)		(3,979)		653		1,658		(3,480)			(5,148)
Gross profit			(231)		(2,456)		(980)		(1,138)		281		(1,575)		(2,555)			(4,987)
Operating expenses:
Selling, general and administrative			(2)		171		502		(107)		10		(2,600)		(29)			(2,726)
Research and development			0		0		(26)		26		0		8		(8)			26
Total operating expenses			(2)		171		476		(81)		10		(2,592)		(37)			(2,700)
Income (loss) from operations			(229)		(2,627)		(1,456)		(1,057)		271		1,017		(2,518)			(2,287)
Interest expense, net			0		0		0		0		0		0		0			0
Amortization of debt discount and prepaid debt costs			0		0		0		0		0		0		0			0
Gain on embedded derivatives and warrants			0		0		0		0		0		0		0			0
Income (loss) from operations before income taxes			(229)		(2,627)		(1,456)		(1,057)		271		1,017		(2,518)			(2,287)
Income tax provision			(54)		0		0		0		0		0		0			0
Net income (loss)			$ (175)		$ (2,627)		$ (1,456)		$ (1,057)		$ 271		$ 1,017		$ (2,518)			$ (2,287)
Net income (loss) per share:
Basic (in dollars per share)			$ (0.01)		$ (0.09)		$ (0.05)		$ (0.04)		$ 0.01		$ 0.03		$ (0.10)			$ (0.08)
Diluted (in dollars per share)			$ (0.01)		$ (0.09)		$ (0.05)		$ (0.04)		$ 0.01		$ 0.03		$ (0.10)			$ (0.08)
Weighted average common shares outstanding:
Basic (in shares)			0		0		0		0									0
Diluted (in shares)			0		0		0		0									0

[1] Includes a non-cash expense for stock-based compensation of $527,000.

[2] Includes a non-cash expense for stock-based compensation of $505,000.

[3] Includes a non-cash expense for stock-based compensation of $770,000.

[4] Includes a non-cash expense for stock-based compensation of $1.3 million.

[5] Includes a non-cash expense for stock-based compensation of $142,000.

[6] Includes a non-cash expense for stock-based compensation of $734,000.

[7] Includes a non-cash expense for stock-based compensation of $789,000 and a $2.6 million charge for the accrual for anticipated settlement of a legal matter.

[8] Includes a gain on embedded derivatives of $1.1 million and a non-cash expense for stock-based compensation of $917,000.