UNAUDITED QUARTERLY FINANCIAL INFORMATION (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 93,530	$ 87,086	$ 85,432	$ 82,971	$ 92,636	$ 80,354	$ 79,464	$ 77,945	$ 349,019	$ 330,399	$ 295,623
Total cost of goods sold	34,588	35,566	36,588	36,416	37,613	36,515	37,293	37,940
Net income (loss)	$ 5,167	$ 2,384	$ (911)	$ (10,474)	$ 9,373	$ (4,156)	$ (6,107)	$ (15,437)	$ (3,834)	$ (16,327)	$ (10,696)
Basic net (loss) income per common share (in dollars per share)	$ 0.07	$ 0.03	$ (0.01)	$ (0.14)	$ 0.13	$ (0.06)	$ (0.09)	$ (0.22)
Diluted net (loss) income per common share (in dollars per share)	$ 0.05	$ 0.03	$ (0.01)	$ (0.14)	$ 0.11	$ (0.06)	$ (0.09)	$ (0.22)