Charges and Credits - Summary of Charges and Credits (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Charges And Credits [Line Items]
Charges and credits, Pretax Charge					$ 228	$ 167
Charges and credits, Tax Benefit					26	28
Charges and credits, Noncontrolling Interests					8	13
Charges and credits, Net					$ 194	$ 126
Interest And Other \| Impairment of Equity Method Investment
Charges And Credits [Line Items]
Charges and credits, Pretax Charge	$ 69
Charges and credits, Tax Benefit	12
Charges and credits, Noncontrolling Interests
Charges and credits, Net	57
Interest And Other \| Workforce reductions
Charges And Credits [Line Items]
Charges and credits, Pretax Charge	66	$ 158	$ 111
Charges and credits, Tax Benefit	3	10	17
Charges and credits, Noncontrolling Interests
Charges and credits, Net	63	148	94
Interest And Other \| Merger and integration-related
Charges And Credits [Line Items]
Charges and credits, Pretax Charge	35	49	31	$ 25
Charges and credits, Tax Benefit	4	1	5	6
Charges and credits, Noncontrolling Interests	4	4	8	5
Charges and credits, Net	27	$ 44	$ 18	$ 14
Interest And Other \| Gain on Sale of Palliser APS Project
Charges And Credits [Line Items]
Charges and credits, Pretax Charge	(149)
Charges and credits, Tax Benefit	(4)
Charges and credits, Noncontrolling Interests
Charges and credits, Net	$ (145)