Mortgage Servicing Rights - Changes in Fair Value of Capitalized MSRs (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Transfers and Servicing of Financial Assets [Abstract]
Balance at beginning of period	$ 3,633	$ 3,707	$ 3,755	$ 2,953
Rights purchased	1	1	3	7
Rights capitalized	106	134	301	473
Rights sold	(292)		(440)	1
Changes in fair value of MSRs
Due to fluctuations in market interest rates	219	153	265	810
Due to revised assumptions or models	16	(5)		(26)
Other changes in fair value	$ (101)	$ (121)	$ (302)	$ (349)
Servicing Asset, Fair Value, Change in Fair Value, Other, Statement of Income or Comprehensive Income [Extensible Enumeration]	Fees and Commissions, Mortgage Banking and Servicing	Fees and Commissions, Mortgage Banking and Servicing	Fees and Commissions, Mortgage Banking and Servicing	Fees and Commissions, Mortgage Banking and Servicing
Balance at end of period	$ 3,582	$ 3,869	$ 3,582	$ 3,869