Employee Benefit Plans (Fair Value Measurements of Plan Assets - Master Retirement Trust) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 11	$ 27	$ 28
Master Trust
Defined Benefit Plan Disclosure [Line Items]
Total assets	9,025	8,324
Master Trust | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	3,199	2,052
Master Trust | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	5,487	5,133
Master Trust | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	11	27
Master Trust | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	328	1,112
Master Trust | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	2,730	2,373
Master Trust | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	2,712	1,751
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	18	622
Master Trust | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	3,999	4,054
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	3,999	4,054
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	545	363
Master Trust | Short-term investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	455	279
Master Trust | Short-term investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	90	84
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	104	120
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	104	120
Master Trust | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Total assets	206	226
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	206	226
Master Trust | Real estate
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	144
Master Trust | Real estate | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Real estate | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Real estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Real estate | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	144
Master Trust | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Total assets	1,231	961
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	1,231	961
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	27
Master Trust | Guaranteed investment contracts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Guaranteed investment contracts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Guaranteed investment contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets	11	27
Master Trust | Guaranteed investment contracts | Not Categorized
Defined Benefit Plan Disclosure [Line Items]
Total assets	0	0
Master Trust | Governments bonds – foreign
Defined Benefit Plan Disclosure [Line Items]
Total assets	78	30
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	78	30
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	75	28
Master Trust | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	75	28
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	46	(2)
Master Trust | Net pending transactions and other investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets	(43)	(6)
Master Trust | Net pending transactions and other investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	89	4
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	50	49
OPEB | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	50	49
OPEB | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	22	25
OPEB | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	22	25
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	9	3
OPEB | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	9	3
OPEB | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total assets	18	20
OPEB | Debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 18	$ 20
Duke Energy Carolinas | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	26.00%	27.00%
Progress Energy | Master Trust
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	31.00%	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%	16.00%
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%