BANK DEPOSITS, Schedule Maturities of Certificates of Deposit (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Scheduled maturities of certificates of deposit, denominations greater than or equal to $100,000 [Abstract]
Three months or less	$ 28	$ 22
Over three through six months	20	21
Over six through twelve months	36	32
Over one through two years	95	93
Over two through three years	18	37
Over three through four years	6	6
Over four through five years	10	9
Total certificates of deposit	213	220
Scheduled maturities of certificates of deposit, denominations less than 100,000 [Abstract]
Three months or less	78	87
Over three through six months	30	76
Over six through twelve months	112	54
Over one through two years	171	170
Over two through three years	160	166
Over three through four years	18	99
Over four through five years	7	6
Total certificates of deposit	$ 576	$ 658