BUSINESS CHANGES AND DEVELOPMENTS - Follow-On Offering (Details) $ / shares in Units, $ in Thousands		1 Months Ended			4 Months Ended	9 Months Ended
	Jan. 11, 2017 shares	Jan. 31, 2017 $ / shares shares	Nov. 30, 2014 USD ($) $ / shares shares	Apr. 30, 2014 shares	Apr. 21, 2014 shares	Dec. 31, 2014 shares	Dec. 31, 2016 shares	Dec. 31, 2015 shares	Oct. 31, 2014
Follow-On Offering
Deferred tax asset attributable to exchanges by partners in connection with follow-on offering | $			$ 80,117
Percentage of tax benefits payable to partners under tax receivable agreement			85.00%
Tax benefit payable to partners under tax receivable agreement in connection with follow-on offering | $			$ 68,099
Period for cash distribution payable to partners under tax receivable agreement for tax benefits			15 years
Class A common stock
Follow-On Offering
Issuance of common stock (in shares)						7,483,442
Number of shares purchased and converted						4,511,058
Common stock, shares outstanding			19,770,893				20,561,108	20,273,118
Class A common stock | Follow-on Offering
Follow-On Offering
Issuance of new and sale of existing common stock (in shares)			6,325,000
Issuance of common stock (in shares)	5,750,000		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
Class B common stock
Follow-On Offering
Issuance of common stock (in shares)				36,158,698	36,158,698
Number of shares purchased and converted						(4,507,453)
Common stock, shares outstanding							31,138,193	31,229,236
Number of shares held by Partner Holdings, parent of the reporting entity			31,621,542
Class B common stock | Follow-on Offering
Follow-On Offering
Number of shares purchased and converted			4,507,453
Number of shares repurchased and retired		5,356,876	1,509,131
Price per share of stock which was repurchased and retired | $ / shares		$ 101	$ 28
Shares converted			2,998,322
Shares issued upon conversion			1,658
Conversion ratio			0.00055
Group LP
Follow-On 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
Follow-On 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 | Follow-on Offering
Follow-On Offering
Number of units acquired by parent			4,509,400
Group LP | Class A common stock
Follow-On Offering
Common stock, shares outstanding							20,561,108