COMMITMENTS AND CONTINGENCIES (Details) - USD ($)	3 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
COMMITMENTS AND CONTINGENCIES
Unfunded capital commitments	$ 586,500,000		$ 535,300,000
Performance Fees
Performance Fees
Performance fees subject to potential clawback provision	451,700,000		418,300,000
Performance fees subject to potential claw back provision that are reimbursable by professionals	350,500,000		323,900,000
EIF Management, LLC
COMMITMENTS AND CONTINGENCIES
Unfunded commitment related to acquisition			20,300,000
Increase (decrease) in contingent consideration liability		$ (20,300,000)
American Capital Ltd. | ARCC
ARCC and American Capital, Ltd. Merger Agreement
Maximum fees waived	$ 10,000,000
Term of fee waiver	30 months
Maximum amount that shortfall will not carry over	$ 10,000,000
Remaining fees waived	$ 90,000,000
Remaining term of fee waiver	27 months
Kayne Anderson Capital Advisors L.P.
COMMITMENTS AND CONTINGENCIES
Unfunded capital commitments	$ 32,400,000		$ 89,200,000