FAIR VALUE MEASUREMENTS - Information about Significant Unobservable Inputs Used for Recurring Fair Value Measurements for Level 3 MSRs (Detail) - Fair Value, Measurements, Recurring - Level 3	3 Months Ended	12 Months Ended
	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
MSR held directly | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Cost to service	$ 89	$ 90
MSR held directly | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Cost to service	103	103
MSR held directly | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Cost to service	94	96
Interests in MSR | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Cost to service	82	78
Interests in MSR | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Cost to service	87	84
Interests in MSR | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Cost to service	$ 84	$ 81
Discount rate | MSR held directly | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.038	0.033
Discount rate | MSR held directly | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.090	0.111
Discount rate | MSR held directly | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.075	0.070
Discount rate | Interests in MSR | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.071	0.084
Discount rate | Interests in MSR | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.071	0.084
Discount rate | Interests in MSR | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.071	0.084
Prepayment rate | MSR held directly | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.055	0.073
Prepayment rate | MSR held directly | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.101	0.159
Prepayment rate | MSR held directly | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.062	0.094
Prepayment rate | Interests in MSR | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.042	0.050
Prepayment rate | Interests in MSR | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.106	0.144
Prepayment rate | Interests in MSR | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.073	0.091
Delinquency rate | MSR held directly | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.001	0.002
Delinquency rate | MSR held directly | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.025	0.025
Delinquency rate | MSR held directly | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.007	0.012
Delinquency rate | Interests in MSR | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.004	0.000
Delinquency rate | Interests in MSR | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.042	0.002
Delinquency rate | Interests in MSR | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
MSR measurement inputs	0.013	0.001