REDEEMABLE CAPITAL STOCK (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended	9 Months Ended
	Oct. 31, 2014 $ / shares shares	Apr. 30, 2014 USD ($) $ / shares shares	Jan. 31, 2014 USD ($) $ / shares shares	Sep. 30, 2014 USD ($) $ / shares	Sep. 30, 2015 shareholder $ / shares shares	Sep. 30, 2014 USD ($) $ / shares	Dec. 31, 2014 $ / shares shares
Redeemable capital stock
Number of newly authorized shares issued upon conversion (in shares) | shares	1
Common shares, par value (in dollars per share) | $ / shares	$ 0.00				$ 0.00		$ 0.00
Stock issued to shareholders several years prior to IPO (in shares) | shares					64,253,037		51,457,023
Change on fair value of redeemable shares				$ 6,916		$ 7,873
Share price (in dollars per share) | $ / shares				$ 13.00		$ 13.00
Amount used for holders of options to acquire common stock						$ 53,400
Two shareholders
Redeemable capital stock
Stock issued to shareholders several years prior to IPO (in shares) | shares					11,050,000
Number of shareholders to whom common stock is issued several years prior to IPO (in shareholders) | shareholder					2
Series A Preferred | T.Rowe Price
Redeemable capital stock
Series A Preferred Stock, issued (in shares) | shares			2,986,229
Share price (in dollars per share) | $ / shares			$ 16.74
Proceeds from issuance of preferred stock			$ 50,000
Amount used for general corporate expenses			20,000
Remaining amount used for distribution to existing holders			30,000
Amount used for distribution to existing holders of common stock			26,900
Amount used for holders of options to acquire common stock			$ 3,100
Series A Preferred | Janus
Redeemable capital stock
Series A Preferred Stock, issued (in shares) | shares		3,225,127
Share price (in dollars per share) | $ / shares		$ 16.74
Proceeds from issuance of preferred stock		$ 54,000
Amount used for general corporate expenses		25,200
Remaining amount used for distribution to existing holders		28,800
Amount used for distribution to existing holders of common stock		26,500
Amount used for holders of options to acquire common stock		$ 2,300