RELATED PARTY TRANSACTIONS (Details) $ in Thousands	3 Months Ended		12 Months Ended	55 Months Ended
	Mar. 31, 2017 USD ($) shares	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) shares	Dec. 31, 2016 USD ($) shares
Related Party Transaction [Line Items]
Accrued fees and other revenue receivable	$ 2,113		$ 2,068	$ 2,068
Equity method investments, at fair value	15,088		14,895	14,895
Available-for-sale securities	$ 21,223		$ 17,009	$ 17,009
Publicly traded common stock (in shares) | shares	2,759,748		2,264,892	2,264,892
Cumulative unrealized gains	$ 700
Percentage of tax benefit under tax receivable agreement	85.00%
MCC Admin Agreement [Member]
Related Party Transaction [Line Items]
Administrative services revenue	$ 1,000	$ 1,100
Accrued fees and other revenue receivable	1,000		$ 900	$ 900
SIC Admin Agreement [Member]
Related Party Transaction [Line Items]
Administrative services revenue	800	600
Accrued fees and other revenue receivable	800		900	900
Funds Admin Agreement [Member]
Related Party Transaction [Line Items]
Administrative services revenue	300	200
Accrued fees and other revenue receivable	300		300	300
Sierra Income Corporation [Member]
Related Party Transaction [Line Items]
Equity method investments, at fair value	9,000		$ 9,000	$ 9,000
Sierra Income Corporation [Member] | Expense Support and Reimbursement Agreement [Member]
Related Party Transaction [Line Items]
Operating expenses percentage			100.00%
Conditional obligation reimbursement period				3 years
Liability for ESA expenses	$ 6,600		$ 7,900	$ 7,900
Expense support and reimbursement agreement expenses		$ 5,200
Common Class A [Member]
Related Party Transaction [Line Items]
Common stock exchange ratio	1