Revenue from contracts with customers transaction price allocated to significant unsatisfied remaining performance obligations and timing of when performance obligations expected to be satisfied (Detail) $ in Millions	Mar. 31, 2024 USD ($)
Electricity, Natural Gas and Fuel [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to remaining performance obligations	$ 22,769
Electricity, Natural Gas and Fuel [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to remaining performance obligations	$ 3,017
Performance obligations expected to be satisfied, period	1 year
Electricity, Natural Gas and Fuel [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to remaining performance obligations	$ 19,752
Performance obligations expected to be satisfied, period
Other Sales and Service Contracts [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to remaining performance obligations	$ 8,428
Other Sales and Service Contracts [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to remaining performance obligations	$ 3,205
Performance obligations expected to be satisfied, period	1 year
Other Sales and Service Contracts [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to remaining performance obligations	$ 5,223
Performance obligations expected to be satisfied, period