Fair Values of Assets and Liabilities - Losses Recognized Related to Nonrecurring Fair Value Measurements of Individual Assets or Portfolios (Detail) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Loans [Member]
Fair Value Assets Measured On Nonrecurring Basis Losses Recognized [Line Items]
Losses recognized related to nonrecurring fair value measurements	$ 71	$ 2	$ 281	$ 35
Other Assets [Member]
Fair Value Assets Measured On Nonrecurring Basis Losses Recognized [Line Items]
Losses recognized related to nonrecurring fair value measurements	$ 1	$ 1	$ 2	$ 12