Employee Benefit Plans (Fair Value Measurements of Plan Assets - Master Retirement Trust) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 0	$ 11	$ 27
Master Trust
Defined Benefit Plan Disclosure [Line Items]
Total assets	9,479	9,025
Master Trust | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	3,541	3,199
Master Trust | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	5,603	5,487
Master Trust | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	11
Master Trust | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	335	328
Master Trust | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	3,202	2,730
Master Trust | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	3,162	2,712
Master Trust | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Equity securities | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	40	18
Master Trust | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	4,162	3,999
Master Trust | Corporate debt securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Corporate debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	4,162	3,999
Master Trust | Corporate debt securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Corporate debt securities | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total assets	397	545
Master Trust | Short-term investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	247	455
Master Trust | Short-term investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	150	90
Master Trust | Short-term investment funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Short-term investment funds | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Total assets	97	104
Master Trust | Partnership interests | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Partnership interests | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Partnership interests | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Partnership interests | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	97	104
Master Trust | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Total assets	198	206
Master Trust | Hedge funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Hedge funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Hedge funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Hedge funds | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	198	206
Master Trust | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Total assets	1,164	1,231
Master Trust | U.S. government bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | U.S. government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	1,164	1,231
Master Trust | U.S. government bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | U.S. government bonds | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Guaranteed investment contracts
Defined Benefit Plan Disclosure [Line Items]
Total assets		11
Master Trust | Guaranteed investment contracts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets		0
Master Trust | Guaranteed investment contracts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets		0
Master Trust | Guaranteed investment contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets		11
Master Trust | Guaranteed investment contracts | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets		0
Master Trust | Governments bonds – foreign
Defined Benefit Plan Disclosure [Line Items]
Total assets	73	78
Master Trust | Governments bonds – foreign | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Governments bonds – foreign | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	73	78
Master Trust | Governments bonds – foreign | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Governments bonds – foreign | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Cash
Defined Benefit Plan Disclosure [Line Items]
Total assets	98	75
Master Trust | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	98	75
Master Trust | Cash | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Cash | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Cash | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Net pending transactions and other investments
Defined Benefit Plan Disclosure [Line Items]
Total assets	88	46
Master Trust | Net pending transactions and other investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	34	(43)
Master Trust | Net pending transactions and other investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	54	89
Master Trust | Net pending transactions and other investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Net pending transactions and other investments | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
OPEB
Defined Benefit Plan Disclosure [Line Items]
Total assets	48	50
OPEB | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	48	50
OPEB | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	23	22
OPEB | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	23	22
OPEB | Real estate
Defined Benefit Plan Disclosure [Line Items]
Total assets	1	1
OPEB | Real estate | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	1	1
OPEB | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total assets	5	9
OPEB | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	5	9
OPEB | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	19	18
OPEB | Debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 19	$ 18
Duke Energy Carolinas | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	26.00%	26.00%
Progress Energy | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	32.00%	31.00%
Duke Energy Progress | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	15.00%	15.00%
Duke Energy Florida | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	17.00%	17.00%
Duke Energy Ohio | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	5.00%	5.00%
Duke Energy Indiana | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	7.00%	7.00%
Piedmont | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	4.00%	4.00%