DEBT - Schedule of outstanding balances and total commitments under Financing Agreements (Details) - USD ($)	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Outstanding balance	$ 894,744,000		$ 887,974,000
Total Commitment	1,471,424,000		1,475,989,000
Secured term loan
Debt Instrument [Line Items]
Outstanding balance	110,000,000		110,000,000
Total Commitment	110,000,000		110,000,000
Wells Fargo Facility
Debt Instrument [Line Items]
Outstanding balance	360,354,000		274,071,000
Total Commitment	500,000,000		500,000,000
Citibank Facility
Debt Instrument [Line Items]
Outstanding balance	126,603,000		184,003,000
Total Commitment	325,000,000		325,000,000
BAML Facility
Debt Instrument [Line Items]
Outstanding balance	36,280,000		36,280,000
Total Commitment	36,280,000		125,000,000
CNB Facility
Debt Instrument [Line Items]
Total Commitment		$ 50,000,000.0
CNB Facility | CNB Facility
Debt Instrument [Line Items]
Outstanding balance	30,500,000		0
Total Commitment	50,000,000	$ 50,000,000	50,000,000
MetLife Facility
Debt Instrument [Line Items]
Outstanding balance	131,807,000		135,145,000
Total Commitment	180,000,000		180,000,000
U.S. Bank Facility
Debt Instrument [Line Items]
Outstanding balance	43,045,000		148,475,000
Total Commitment	185,989,000		185,989,000
Notes Payable
Debt Instrument [Line Items]
Outstanding balance	56,155,000		0
Total Commitment	$ 84,155,000		$ 0