Leases (Narrative) (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2024	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020
Leases Disclosure [Line Items]
Property, plant and equipment			$ 68,862	$ 58,780
Accumulated depreciation and amortization			25,982	24,637
Payment of settlement of an agreement related to the offshore wind installation vessel under development	$ 47
Charge in connection with settlement of an agreement		$ 47
Charge in connection with settlement of an agreement, after tax		$ 35
Agreement with Lessor to Complete Construction and Lease Jones Act Compliant Offshore Wind Installation Vessel
Leases Disclosure [Line Items]
Requested cash draws from lessor to fund project costs			$ 598
Required percentage payment for specific full recourse events						100.00%
Lease agreement maturity period			5 years
Lessor | Agreement with Lessor to Complete Construction and Lease Jones Act Compliant Offshore Wind Installation Vessel
Leases Disclosure [Line Items]
Amount of financing commitments to fund estimated project costs						$ 715
Power Purchase Arrangement [Member]
Leases Disclosure [Line Items]
Property, plant and equipment			$ 382	382
Accumulated depreciation and amortization			38	28
Rental revenue			$ 18	$ 21	$ 16
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]			Revenues	Revenues	Revenues
Depreciation expense			$ 10	$ 10	$ 34