COMMITMENTS, CONTINGENCIES AND GUARANTEES, Commitments and Contingencies (Details) $ in Millions	3 Months Ended
	Dec. 31, 2020 USD ($) agreement
Underwriting commitment
Commitments [Line Items]
Number of open underwriting commitments | agreement	1
Independent venture capital or private equity investment commitment
Commitments [Line Items]
Amount of commitment	$ 34
Commitment to lend to RJTCF
Commitments [Line Items]
Amount of commitment	$ 120
Number of days that investments in project partnerships typically sold	90 days
Forward GNMA MBS purchase commitments
Commitments [Line Items]
Amount of commitment	$ 318
Expected time of purchase (in days)	90 days