STOCKHOLDERS' EQUITY (Details)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Stockholders' Equity
Shares issued pursuant to stock option exercises	16,458	2,897
Restricted common stock
Stockholders' Equity
Shares vested	542,121	303,016
Shares held to satisfy the employees' tax liability	84,224	41,934
Restricted common stock | Employees
Stockholders' Equity
Unvested shares of restricted Common Stock forfeited	37,275	27,965
Shares granted	642,000	954,000
Restricted common stock | Board of directors
Stockholders' Equity
Shares granted	71,205	54,879
Number of members of the board of directors to whom grants were made	3	3