DEBT OBLIGATIONS AND CREDIT FACILITIES - Credit Facilities of Consolidated Funds (Details) - Consolidated VIEs	3 Months Ended
Mar. 31, 2020 USD ($)	Mar. 31, 2020 EUR (€)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,062,792,000
Total debt obligations, net	5,230,605,000		$ 5,767,999,000
Credit Agreement
Debt Instrument [Line Items]
Long-term debt, gross	263,300,000		159,400,000
Less: Debt issuance costs	(1,250,000)		(934,000)
Total debt obligations, net	262,022,000		158,477,000
Credit Agreement \| Revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 75,961,000		0
Facility Capacity \| €		€ 120,000,000
Weighted Average Interest Rate	1.99%	1.99%
Weighted Average Remaining Maturity (years)	2 years 9 months 18 days
Commitment Fee Rate	0.20%
Line Of Credit Facility, LC Fee Percentage	1.50%
Credit Agreement \| Senior variable rate notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 187,311,000		$ 159,411,000
Facility Capacity	$ 187,311,000
Weighted Average Interest Rate	2.77%	2.77%
Weighted Average Remaining Maturity (years)	7 years 1 month 6 days

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- Definition

Line Of Credit Facility, LC Fee Percentage

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Weighted average interest rate of debt outstanding.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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