Mortgage Servicing Rights - MSRs and Related Characteristics by Portfolio (Detail) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023 USD ($) BasisPoint Multiple	Dec. 31, 2022 USD ($) BasisPoint Multiple	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Servicing Assets at Fair Value [Line Items]
Fair value	$ 3,724	$ 3,755	$ 3,432	$ 2,953
Mortgage Servicing Rights [Member]
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	241,718	239,753
Fair value	$ 3,724	$ 3,755
Value (bps) | BasisPoint	154	157
Weighted-average servicing fees (bps) | BasisPoint	30	30
Multiple (value/servicing fees) | Multiple	5.08	5.2
Weighted-average note rate	3.74%	3.67%
Weighted-average age (in years)	4 years 1 month 6 days	3 years 10 months 24 days
Weighted-average expected prepayment (constant prepayment rate)	8.40%	7.80%
Weighted-average expected life (in years)	7 years 6 months	7 years 8 months 12 days
Weighted-average option adjusted spread	5.70%	5.80%
HFA [Member] | Mortgage Servicing Rights [Member]
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	$ 44,746	$ 44,071
Fair value	$ 716	$ 725
Value (bps) | BasisPoint	160	165
Weighted-average servicing fees (bps) | BasisPoint	36	36
Multiple (value/servicing fees) | Multiple	4.44	4.56
Weighted-average note rate	4.24%	4.16%
Weighted-average age (in years)	4 years 1 month 6 days	4 years
Weighted-average expected prepayment (constant prepayment rate)	8.00%	7.40%
Weighted-average expected life (in years)	8 years 6 months	8 years 9 months 18 days
Weighted-average option adjusted spread	7.60%	7.60%
Government Insured [Member] | Mortgage Servicing Rights [Member]
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	$ 23,695	$ 23,141
Fair value	$ 454	$ 454
Value (bps) | BasisPoint	192	196
Weighted-average servicing fees (bps) | BasisPoint	43	42
Multiple (value/servicing fees) | Multiple	4.5	4.69
Weighted-average note rate	3.92%	3.81%
Weighted-average age (in years)	5 years 6 months	5 years 8 months 12 days
Weighted-average expected prepayment (constant prepayment rate)	9.50%	8.50%
Weighted-average expected life (in years)	7 years 3 months 18 days	7 years 7 months 6 days
Weighted-average option adjusted spread	6.90%	6.90%
Conventional [Member] | Mortgage Servicing Rights [Member]
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	$ 173,277	$ 172,541
Fair value	$ 2,554	$ 2,576
Value (bps) | BasisPoint	147	149
Weighted-average servicing fees (bps) | BasisPoint	27	27
Multiple (value/servicing fees) | Multiple	5.42	5.52
Weighted-average note rate	3.59%	3.52%
Weighted-average age (in years)	3 years 10 months 24 days	3 years 8 months 12 days
Weighted-average expected prepayment (constant prepayment rate)	8.40%	7.80%
Weighted-average expected life (in years)	7 years 3 months 18 days	7 years 6 months
Weighted-average option adjusted spread	4.90%	5.10%