Charges and Credits - Summary of Charges and Credits (Detail) - USD ($)	3 Months Ended					9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2024
Charges And Credits [Line Items]
Charges and credits, Pretax Charge						$ 279,000,000
Charges and credits, Tax Benefit						48,000,000
Charges and credits, Noncontrolling Interests						20,000,000
Charges and credits, Net				$ 0	$ 0	$ 211,000,000
Interest And Other | Workforce reductions
Charges And Credits [Line Items]
Charges and credits, Pretax Charge	$ 65,000,000	$ 111,000,000
Charges and credits, Tax Benefit	10,000,000	17,000,000
Charges and credits, Net	55,000,000	94,000,000
Interest And Other | Merger & integration
Charges And Credits [Line Items]
Charges and credits, Pretax Charge	47,000,000	31,000,000	$ 25,000,000
Charges and credits, Tax Benefit	10,000,000	5,000,000	6,000,000
Charges and credits, Noncontrolling Interests	7,000,000	8,000,000	5,000,000
Charges and credits, Net	$ 30,000,000	$ 18,000,000	$ 14,000,000