BANK LOANS, NET, Allowance for Loan Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Mar. 31, 2025	Sep. 30, 2025
SBL
Net (charge-offs)/recoveries:
Charge-offs	$ 0		$ 0
C&I loans
Net (charge-offs)/recoveries:
Charge-offs	(1)		(33)
CRE loans
Net (charge-offs)/recoveries:
Charge-offs	(8)		(12)
REIT loans
Net (charge-offs)/recoveries:
Charge-offs	0		0
Residential mortgage loans
Net (charge-offs)/recoveries:
Charge-offs	0		(1)
Tax-exempt loans
Net (charge-offs)/recoveries:
Charge-offs	0		0
Total loans held for investment
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	452	$ 457	457
Provision/(benefit) for credit losses	(3)	0
Net (charge-offs)/recoveries:
Charge-offs	(9)	(4)
Recoveries	0	0
Net charge-offs	(9)	(4)
Foreign exchange translation adjustment	0	(1)
Balance at end of period	$ 440	$ 452
ACL by loan portfolio segment as a % of total ACL	100.00%	100.00%
Decrease in allowance for credit losses	$ 12
Total loans held for investment | SBL
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	8	$ 6	6
Provision/(benefit) for credit losses	(1)	(1)
Net (charge-offs)/recoveries:
Charge-offs	0	0
Recoveries	0	0
Net charge-offs	0	0
Foreign exchange translation adjustment	0	0
Balance at end of period	$ 7	$ 5
ACL by loan portfolio segment as a % of total ACL	1.60%	1.10%
Total loans held for investment | C&I loans
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	$ 148	$ 173	173
Provision/(benefit) for credit losses	(1)	7
Net (charge-offs)/recoveries:
Charge-offs	(1)	(4)
Recoveries	0	0
Net charge-offs	(1)	(4)
Foreign exchange translation adjustment	0	0
Balance at end of period	$ 146	$ 176
ACL by loan portfolio segment as a % of total ACL	33.20%	38.90%
Total loans held for investment | CRE loans
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	$ 182	$ 188	188
Provision/(benefit) for credit losses	2	(10)
Net (charge-offs)/recoveries:
Charge-offs	(8)	0
Recoveries	0	0
Net charge-offs	(8)	0
Foreign exchange translation adjustment	0	(1)
Balance at end of period	$ 176	$ 177
ACL by loan portfolio segment as a % of total ACL	40.00%	39.20%
Total loans held for investment | REIT loans
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	$ 52	$ 23	23
Provision/(benefit) for credit losses	(4)	4
Net (charge-offs)/recoveries:
Charge-offs	0	0
Recoveries	0	0
Net charge-offs	0	0
Foreign exchange translation adjustment	0	0
Balance at end of period	$ 48	$ 27
ACL by loan portfolio segment as a % of total ACL	10.90%	6.00%
Total loans held for investment | Residential mortgage loans
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	$ 61	$ 65	65
Provision/(benefit) for credit losses	1	0
Net (charge-offs)/recoveries:
Charge-offs	0	0
Recoveries	0	0
Net charge-offs	0	0
Foreign exchange translation adjustment	0	0
Balance at end of period	$ 62	$ 65
ACL by loan portfolio segment as a % of total ACL	14.10%	14.40%
Total loans held for investment | Tax-exempt loans
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	$ 1	$ 2	$ 2
Provision/(benefit) for credit losses	0	0
Net (charge-offs)/recoveries:
Charge-offs	0	0
Recoveries	0	0
Net charge-offs	0	0
Foreign exchange translation adjustment	0	0
Balance at end of period	$ 1	$ 2
ACL by loan portfolio segment as a % of total ACL	0.20%	0.40%
Unfunded lending commitments
Net (charge-offs)/recoveries:
Allowance, unfunded lending commitment	$ 24			$ 24