UPDATE OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings reduction	$ (7,438)	$ (7,176)	$ (6,903)
C&I and REIT Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reversion period	1 year
CRE and Residential Mortgage Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reversion period, completion	5 years
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Repayment term	5 years
Forecast period	2 years
Minimum | CRE and Residential Mortgage Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reversion period	2 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Repayment term	10 years
Forecast period	3 years
Maximum | CRE and Residential Mortgage Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reversion period	3 years
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings reduction	$ (6,702)	(6,484)	$ (6,086)	$ (5,874)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowances for credit losses, including unfunded lending commitments		45
Cumulative Effect, Period of Adoption, Adjustment | Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings reduction		$ 35		$ 0