Investment Securities - Gross Unrealized Losses and Fair Value of Company's Investment Securities (Detail) $ in Millions	Jun. 30, 2022 USD ($)
Continuous Gross Unrealized Losses And Fair Value [Abstract]
Fair Value Less Than 12 Months	$ 83,697
Unrealized Losses Less Than 12 Months	(7,576)
Fair Value 12 Months or Greater	11,978
Unrealized Losses 12 Months or Greater	(1,907)
Fair Value Total	95,675
Unrealized Losses Total	(9,483)
U.S. Treasury and Agencies [Member]
Continuous Gross Unrealized Losses And Fair Value [Abstract]
Fair Value Less Than 12 Months	19,590
Unrealized Losses Less Than 12 Months	(1,581)
Fair Value 12 Months or Greater	3,511
Unrealized Losses 12 Months or Greater	(431)
Fair Value Total	23,101
Unrealized Losses Total	(2,012)
Residential Mortgage-Backed Securities [Member]
Continuous Gross Unrealized Losses And Fair Value [Abstract]
Fair Value Less Than 12 Months	50,819
Unrealized Losses Less Than 12 Months	(4,281)
Fair Value 12 Months or Greater	5,360
Unrealized Losses 12 Months or Greater	(778)
Fair Value Total	56,179
Unrealized Losses Total	(5,059)
Commercial Mortgage Backed Securities [Member]
Continuous Gross Unrealized Losses And Fair Value [Abstract]
Fair Value Less Than 12 Months	4,852
Unrealized Losses Less Than 12 Months	(657)
Fair Value 12 Months or Greater	2,711
Unrealized Losses 12 Months or Greater	(535)
Fair Value Total	7,563
Unrealized Losses Total	(1,192)
Obligations of State and Political Subdivisions [Member]
Continuous Gross Unrealized Losses And Fair Value [Abstract]
Fair Value Less Than 12 Months	8,430
Unrealized Losses Less Than 12 Months	(1,057)
Fair Value 12 Months or Greater	396
Unrealized Losses 12 Months or Greater	(163)
Fair Value Total	8,826
Unrealized Losses Total	(1,220)
Other [Member]
Continuous Gross Unrealized Losses And Fair Value [Abstract]
Fair Value Less Than 12 Months	6
Fair Value Total	$ 6