Equity (Narrative) (Detail)	1 Months Ended													3 Months Ended					12 Months Ended
	Dec. 31, 2020 USD ($) shares	Nov. 30, 2020 USD ($) shares	Sep. 30, 2020 USD ($) agreement shares	Aug. 31, 2020 USD ($) shares	Mar. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($)	Oct. 31, 2019	Aug. 31, 2019 USD ($) shares	Jan. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Jun. 30, 2018 USD ($) shares	Apr. 30, 2018 shares	Jan. 31, 2018 USD ($) shares	Dec. 31, 2020 USD ($) shares	Sep. 30, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Mar. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Jul. 31, 2020 USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock								$ 1,400,000,000											$ 159,000,000	$ 2,515,000,000	$ 2,461,000,000
Issuance of common stock (in shares) | shares			4,100,000					18,500,000												6,100,000
Acquisition of SCANA																				$ 6,818,000,000
Amount of income taxes recognized in equity primarily attributable to establishing additional regulatory liabilities																				(40,000,000)
Defined Benefit Pension plans																				499,000,000
Fees and commissions paid																				28,000,000
Stock repurchased, shares | shares			4,100,000
Stock repurchased, value			$ 323,000,000																3,080,000,000
Number of prepaid accelerated share repurchase agreements | agreement			2
Accelerated share repurchase, payments	$ 400,000,000		$ 1,500,000,000											$ 400,000,000	$ 1,500,000,000				$ 400,000,000
Accelerated share repurchase, cash paid for number of shares exchange | shares	5,000,000.0		17,200,000											5,000,000.0	17,200,000				5,000,000.0
Decrease in common stock	$ 400,000,000	$ 1,500,000,000
Common stock worth based on closing Price	$ 400,000,000		$ 1,500,000,000											$ 400,000,000	$ 1,500,000,000				$ 400,000,000
Accelerated share repurchase, additional shares delivered under terms of the agreement | shares	300,000	1,400,000												300,000					300,000
Number of shares received | shares											27,000,000
Increase (decrease) Non-controlling interest											$ 375,000,000
Compensation cost related to stock-based compensation																			$ 64,000,000	46,000,000	48,000,000
Tax benefit from stock awards and stock options exercised																			$ 16,000,000	11,000,000	12,000,000
Vesting period																			3 years
Cash Based Performance Grant | Officer
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cash-based performance grants minimum percentage																			0.00%
Cash-based performance grants maximum percentage																			200.00%
February2018 Cash Based Performance Grant | Officer
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Targeted amount of the grant	$ 15,000,000													$ 15,000,000					$ 15,000,000
February2019 Cash Based Performance Grant | Officer | Grant Date Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Targeted amount of the grant	15,000,000													15,000,000					15,000,000
Liability accrued for award	14,000,000													14,000,000					14,000,000
February 2020 Cash Based Performance Grant | Officer | Grant Date Three
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Targeted amount of the grant	16,000,000													16,000,000					16,000,000
Liability accrued for award	$ 8,000,000													$ 8,000,000					$ 8,000,000
Stock Based Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares were available for future grants | shares	20,000,000													20,000,000					20,000,000
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested awards	$ 61,000,000													$ 61,000,000					$ 61,000,000
Fair value of restricted stock awards that vested																			$ 35,000,000	$ 23,000,000	$ 23,000,000
Cove Point
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Ownership interest percentage of limited partner interests						25.00%	25.00%
Cash consideration from sale of noncontrolling interest						$ 2,100,000,000
Cove Point | GT&S Transaction
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Controlling interest sold		25.00%
Ownership percentage		50.00%
Reversal of noncontrolling interest held by noncontrolling owners		$ 1,400,000,000
Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock (in shares) | shares																			7,000,000	39,000,000	36,000,000
Acquisition of SCANA (in shares) | shares																				96,000,000
Acquisition of SCANA																				$ 6,818,000,000
Amount of income taxes recognized in equity primarily attributable to establishing additional regulatory liabilities																				1,181,000,000
Defined Benefit Pension plans																				499,000,000
Fees and commissions paid																				$ 14,000,000
Stock repurchased, shares | shares																			38,900,000	0	0
Stock repurchased, value		$ 1,000,000,000.0																	$ 3,080,000,000
Stock repurchase program, authorized amount																						$ 3,000,000,000.0
Common Stock | Open Market Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock repurchased, shares | shares														3,700,000	7,200,000
Stock repurchased, value														$ 295,000,000	$ 562,000,000
Goldman Sachs & Co. and Credit Suisse LLC.
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock										$ 1,400,000,000
Issuance of common stock (in shares) | shares										22,100,000
Number of shares for future agreement | shares												20,000,000
Option exercised | shares												2,100,000
Maximum | Stock Based Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum term of stock based awards																			8 years
Weighted Average | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected weighted-average period recognized for the unrecognized compensation cost																			2 years
Dominion Energy Midstream Partners, LP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Acquisition of SCANA (in shares) | shares									22,500,000
Acquisition of SCANA									$ 1,600,000,000
Common units conversion ratio									0.2492
Gain or loss recognized in equity transaction									$ 0
Amount of income taxes recognized in equity primarily attributable to establishing additional regulatory liabilities									$ 40,000,000
Dominion Energy Direct
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock																			$ 159,000,000
Issuance of common stock (in shares) | shares																			2,100,000
SCANA
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Acquisition of SCANA (in shares) | shares									95,600,000											95,600,000
Acquisition of SCANA									$ 6,800,000,000											$ 6,800,000,000
Various Programs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock																			$ 481,000,000,000	$ 11,000,000,000.0	$ 2,500,000,000
Issuance of common stock (in shares) | shares																			7,000,000	157,000,000	36,000,000
Sales Agency Agreements to Effect Sales Under At-the-market Program
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock													$ 495,000,000			$ 639,000,000	$ 154,000,000	$ 197,000,000
Issuance of common stock (in shares) | shares				0	0								6,600,000			7,800,000	2,100,000	2,700,000
Fees and commissions paid													$ 5,000,000			$ 6,000,000	$ 2,000,000	$ 2,000,000
Sale of stock authorized amount					$ 500,000,000
Sales Agency Agreements to Effect Sales Under At-the-market Program | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale of stock authorized amount				$ 1,000,000,000.0
Underwriting Agreement | Goldman Sachs & Co. and Credit Suisse LLC.
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares for future agreement | shares												3,000,000