LOAN SERVICING - Sensitivity of Fair Value to Changes in key Assumptions (Detail) - Mortgage Servicing Rights [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Weighted average life (months)	62 months 10 days	78 months 27 days
Constant prepayment rate (annualized)	14.50%	10.60%
Discount rate	9.60%	9.70%
Sensitivity analysis of fair value, change in interest rates, plus .25%	$ 2	$ 3
Sensitivity analysis of fair value, change in interest rates, plus .50%	5	5
Sensitivity analysis of fair value, change in interest rates, minus .25%	(2)	(3)
Sensitivity analysis of fair value, change in interest rates, minus .50%	$ (3)	$ (5)