Asset Retirement Obligations (ARO by Category) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Asset Retirement Obligations [Line Items]
Total ARO	$ 10,469	$ 10,175
Less: current portion	716	689
Total noncurrent ARO	9,753	9,486
Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,819	3,610
Less: current portion	227	337
Total noncurrent ARO	3,592	3,273
Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	5,438	5,414
Less: current portion	386	295
Total noncurrent ARO	5,052	5,119
Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,835	4,673
Less: current portion	381	295
Total noncurrent ARO	4,454	4,378
Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	602	742
Less: current portion	5	0
Total noncurrent ARO	597	742
Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	89	84
Less: current portion	5	3
Total noncurrent ARO	84	81
Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	856	781
Less: current portion	98	54
Total noncurrent ARO	758	727
Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	15	15
Total noncurrent ARO	15	$ 15
Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligations [Line Items]
Total ARO	5,319
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,002
Decommissioning of Nuclear Power Facilities [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,158
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,621
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	536
Closure of Ash Impoundments [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,843
Closure of Ash Impoundments [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	1,761
Closure of Ash Impoundments [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,202
Closure of Ash Impoundments [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,178
Closure of Ash Impoundments [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	24
Closure of Ash Impoundments [Member] | Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	44
Closure of Ash Impoundments [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	836
Other [Member]
Asset Retirement Obligations [Line Items]
Total ARO	307
Other [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	56
Other [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	78
Other [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	36
Other [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	42
Other [Member] | Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	45
Other [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	20
Other [Member] | Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	$ 15