COMMITMENTS AND CONTINGENCIES - Contingent Repayment Guarantees (Details)	Sep. 30, 2018 USD ($)
Contingent Repayment Guarantees
Private equity fund carried interest amount subject to clawback provision assuming liquidation at fair value	$ 0
Liquidation value for clawback obligation	0
Clawback obligation amount if private equity vehicles liquidated at fair value	2,000,000,000
Private Equity
Investment Commitments
Unfunded commitments	5,055,900,000
Principal Activities
Investment Commitments
Unfunded commitments	28,600,000
Capital Markets
Investment Commitments
Unfunded commitments	$ 1,041,700,000