Unaudited Quarterly Financial Information (Details) (USD $)	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Income (Loss) [Abstract]
Revenue	$ 38,979,000		$ 51,197,000		$ 55,610,000		$ 47,748,000		$ 44,503,000		$ 42,713,000		$ 36,238,000		$ 35,804,000		$ 193,534,000	$ 159,258,000	$ 147,176,000
Gross profit	14,374,000		21,113,000		21,576,000		18,230,000		17,229,000		18,142,000		14,524,000		15,157,000		75,293,000	65,052,000	57,070,000
Net income (loss)	(2,814,000)	[1]	6,027,000	[2]	3,405,000	[3]	(278,000)	[4]	2,867,000	[5]	5,228,000	[6]	31,000	[7]	(952,000)	[8]	6,340,000	7,174,000	(1,438,000)
Basic and diluted net income (loss) per share	$ (0.10)		$ 0.21		$ 0.12		$ (0.01)		$ 0.10		$ 0.18		$ 0.00		$ (0.03)
Stock-based compensation expense	$ 1,358,000		$ 719,000		$ 946,000		$ 1,000,000		$ 527,000		$ 505,000		$ 770,000		$ 1,286,000		$ 3,980,000	$ 3,088,000	$ 2,582,000

[1] Includes a non-cash expense for stock-based compensation of $1.4 million.

[2] Includes a non-cash expense for stock-based compensation of $719,000.

[3] Includes a non-cash expense for stock-based compensation of $946,000.

[4] Includes a non-cash expense for stock-based compensation of $1.0 million.

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

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

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

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