Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Detail) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020
Significant noncash investing and financing activities:
Accrued capital expenditures		$ 327	$ 346
Accrued contributions to equity method affiliates		20	5
Leases	[1]	29	35
Financing leases		22	32
Virginia Electric and Power Company
Significant noncash investing and financing activities:
Accrued capital expenditures		207	239
Financing leases		$ 17	$ 20

[1] Includes $22 million and $32 million of financing leases at June 30, 2021 and 2020, respectively, and $7 million and $3 million of operating leases at June 30, 2021 and 2020, respectively.