STOCKHOLDERS’ EQUITY / DEFICIT - (Details) - USD ($)			1 Months Ended					6 Months Ended	12 Months Ended
	Mar. 24, 2015	May. 09, 2014	Mar. 31, 2015	Jan. 31, 2014	Aug. 31, 2013	Feb. 28, 2013	Jan. 31, 2013	Aug. 18, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 08, 2015
Stockholders Equity [Line Items]
Common stock, shares authorized									100,000,000	100,000,000
Common stock, par value (in dollars per share)									$ 0.0001	$ 0.0001
Common stock per shares are entitled to vote									1 vote
Preferred stock, par value (in dollars per share)									$ 0.001	$ 0.001
Preferred Stock, shares authorized									20,000,000	20,000,000
Price per common share (in dollars per share)			$ 19.00	$ 8.50	$ 4.50	$ 3.00	$ 3.00
Net proceeds from the offering									$ 149,487,000	$ 40,000,000	$ 30,937,000
Underwriting fees and other offering costs			$ 9,000,000	$ 3,200,000	$ 2,800,000	$ 900,000	$ 0
2014 Incentive Compensation Plan
Stockholders Equity [Line Items]
Shares issued (in shares)		3,000,000.0
2015 Equity Incentive Plan
Stockholders Equity [Line Items]
Common stock, shares authorized												1,400,000.0
Shares remaining available for issuance under the plan (in shares)												600,000.0
Series A Preferred Stock
Stockholders Equity [Line Items]
Preferred stock, par value (in dollars per share)									$ 0.001
Preferred Stock, shares authorized									1,000
Restricted shares
Stockholders Equity [Line Items]
Issuance of stock options to purchase shares (in shares)								230,000
Restricted shares | 2014 Incentive Compensation Plan
Stockholders Equity [Line Items]
Issuance of stock options to purchase shares (in shares)								230,000
Stock Options
Stockholders Equity [Line Items]
Shares issued (in shares)									2,285,000
Common Stock
Stockholders Equity [Line Items]
Shares issued (in shares)									478,334
Issuance of stock options to purchase shares (in shares)								1,928,000
Common Stock | 2014 Incentive Compensation Plan
Stockholders Equity [Line Items]
Issuance of stock options to purchase shares (in shares)								1,928,000
Public Offering | Common Stock
Stockholders Equity [Line Items]
Number of common stock issued	7,866,000
Price per common share (in dollars per share)	$ 19.00
Net proceeds from the offering	$ 140,000,000
Underwriting fees and other offering costs	$ 9,500,000