Unaudited Supplementary Quarterly Financial Information (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
Unaudited Supplementary Quarterly Financial Information
Total revenue	$ 24,248	$ 24,165	$ 27,187	$ 25,281	$ 26,405	$ 25,048	$ 27,396	$ 23,594	$ 100,881	$ 102,443	$ 88,545
Gross profit	8,442	8,812	9,460	8,565	9,906	9,366	10,827	8,598	35,279	38,697	32,075
Net income (loss)	$ 345	$ 793	$ 134	$ 175	$ (1,906)	$ 1,545	$ 395	$ 310	$ 1,447	$ 344	$ (23,572)
Basic income (loss) per share	$ 0.03	$ 0.07	$ 0.01	$ 0.02	$ (0.17)	$ 0.13	$ 0.03	$ 0.03	$ 0.13	$ 0.03	$ (1.93)
Diluted income (loss) per share	$ 0.03	$ 0.07	$ 0.01	$ 0.02	$ (0.17)	$ 0.13	$ 0.03	$ 0.03	$ 0.13	$ 0.03	$ (1.93)