Unaudited Quarterly Financial Information (Details) (USD $)	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
Operating Income (Loss) [Abstract]
Revenue	$ 44,503,000		$ 42,713,000		$ 36,238,000		$ 35,804,000		$ 37,376,000		$ 42,030,000		$ 38,546,000		$ 29,224,000		$ 159,258,000	$ 147,176,000	$ 121,882,000
Gross profit	17,229,000		18,142,000		14,524,000		15,157,000		15,010,000		16,830,000		13,901,000		11,329,000		65,052,000	57,070,000	46,887,000
Net income (loss)	2,867,000	[1]	5,228,000	[2]	31,000	[3]	(952,000)	[4]	515,000	[5]	569,000	[6]	(200,000)	[7]	(2,322,000)	[8]	7,174,000	(1,438,000)	(6,056,000)
Basic and diluted net income (loss) per share	$ 0.10		$ 0.18		$ 0.00		$ (0.03)		$ 0.02		$ 0.02		$ (0.01)		$ (0.09)
Stock-based compensation expense	527,000		505,000		770,000		1,300,000		142,000		734,000		789,000		917,000		3,088,000	2,582,000	2,627,000
Gain on embedded derivatives and warrants			0		0		0		0		0		0		1,086,000		0	1,086,000	2,341,000
Charge for the accrual for anticipated settlement of a legal matter													$ 2,600,000

[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.