Asset Retirement Obligations (ARO by Category) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Asset Retirement Obligations [Line Items]
Total ARO	$ 10,256	$ 10,175
Less: current portion	902	689
Total noncurrent ARO	9,354	9,486
Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,712	3,610
Less: current portion	292	337
Total noncurrent ARO	3,420	3,273
Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	5,435	5,414
Less: current portion	475	295
Total noncurrent ARO	4,960	5,119
Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,841	4,673
Less: current portion	470	295
Total noncurrent ARO	4,371	4,378
Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	593	742
Less: current portion	4
Total noncurrent ARO	589	742
Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	98	84
Less: current portion	7	3
Total noncurrent ARO	91	81
Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	744	781
Less: current portion	128	54
Total noncurrent ARO	616	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	5,367
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,031
Decommissioning of Nuclear Power Facilities [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,181
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,650
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	531
Closure of Ash Impoundments [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,575
Closure of Ash Impoundments [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	1,623
Closure of Ash Impoundments [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,175
Closure of Ash Impoundments [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,154
Closure of Ash Impoundments [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	20
Closure of Ash Impoundments [Member] | Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	52
Closure of Ash Impoundments [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	725
Other [Member]
Asset Retirement Obligations [Line Items]
Total ARO	314
Other [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	58
Other [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	79
Other [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	37
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	46
Other [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	19
Other [Member] | Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	$ 15