BUSINESS CHANGES AND DEVELOPMENTS (Details 3) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended
	Nov. 30, 2014 USD ($) $ / shares shares	Apr. 30, 2014 shares	Sep. 30, 2015 shares	Dec. 31, 2014 shares	Oct. 31, 2014
Secondary Offering
Deferred tax asset attributable to exchanges by partners in connection with secondary offering | $	$ 80,117
Percentage of tax benefits payable to partners under tax receivable agreement	85.00%		85.00%
Tax benefit payable to partners under tax receivable agreement in connection with secondary offering | $	$ 68,099
Period for cash distribution payable to partners under tax receivable agreement for tax benefits	15 years
Class A common stock
Secondary Offering
Common stock, shares outstanding	19,770,893		20,158,230	19,770,893
Class A common stock | Secondary Offering
Secondary Offering
Issuance of new and sale of existing common stock (in shares)	6,325,000
Issuance of common stock (in shares)	4,509,400
Number of existing shares sold during the period by current holders to new investors	1,815,600
Number of shares purchased and converted	4,511,058
Shares issued upon conversion	1,658
Class B common stock
Secondary Offering
Issuance of common stock (in shares)		36,158,698
Common stock, shares outstanding			31,358,729	31,621,542
Number of shares held by Partner Holdings, parent of the reporting entity	31,621,542
Class B common stock | Secondary Offering
Secondary Offering
Number of shares purchased and converted	4,507,453
Number of shares repurchased and retired	1,509,131
Price per share of stock which was repurchased and retired | $ / shares	$ 28
Shares converted	2,998,322
Conversion ratio	0.00055
Group LP
Secondary Offering
Limited partnership interest held by parent (as a percent)	36.00%				28.00%
Limited partnership interest held by noncontrolling interest (as a percent)	64.00%				72.00%
Group LP | Class A partnership units
Secondary Offering
Number of limited partner units held by parent	19,770,893
Number of limited partner units held by noncontrolling interests	34,479,961
Group LP | Class A partnership units | Secondary Offering
Secondary Offering
Number of units acquired by parent	4,509,400
Group LP | Class A common stock
Secondary Offering
Common stock, shares outstanding			20,158,230