FAIR VALUE MEASUREMENTS - Rollforward on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 24	$ 3
Purchases, issuances, sales and settlements:
Issuances	13	24
Settlements	(24)	(3)
Balance at end of period	13	24
Interest Rate Lock Commitments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	24	3
Purchases, issuances, sales and settlements:
Issuances	13	24
Settlements	(24)	(3)
Balance at end of period	$ 13	$ 24