COMMITMENTS AND CONTINGENCIES - Leases: Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Operating lease liabilities	$ 214,681
Finance lease obligations	977
Accumulated amortization	$ 1,400	$ 1,000
Finance lease assets [Extensible List]	Other assets
Finance lease, liability [Extensible List]	Accounts Payable and Accrued Liabilities
Ares Management L.P
Lessee, Lease, Description [Line Items]
Operating lease assets	$ 176,511	154,742
Finance lease assets	1,164	1,386
Total lease assets	177,675	156,128
Operating lease liabilities	214,681	180,236
Finance lease obligations	977	1,273
Total lease liabilities	$ 215,658	$ 181,509
Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term	12 years