FAIR VALUE MEASUREMENTS - Rollforward on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 9	$ 24
Purchases, issuances, sales and settlements:
Purchases	2
Issuances		9
Settlements	(9)	(24)
Balance at end of period	2	9
Other debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	0	0
Purchases, issuances, sales and settlements:
Purchases	2
Issuances		0
Settlements	0	0
Balance at end of period	2	0
Interest rate lock commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	9	24
Purchases, issuances, sales and settlements:
Purchases	0
Issuances		9
Settlements	(9)	(24)
Balance at end of period	$ 0	$ 9