Leases (Lease Costs) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		$ 136
Operating lease expense	$ 73	145
Short-term lease expense	6	13
Variable lease expense	10	21
Finance lease expense
Amortization of leased assets	29	56
Interest on lease liabilities	20	37
Total finance lease expense	49	93
Total lease expense	138	272
Operating cash flows from finance leases		37
Financing cash flows from finance leases		56
Finance		175
Operating		78
Duke Energy Carolinas [Member]
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		15
Operating lease expense	11	23
Short-term lease expense	2	4
Variable lease expense	4	12
Finance lease expense
Amortization of leased assets	1	2
Interest on lease liabilities	3	7
Total finance lease expense	4	9
Total lease expense	21	48
Operating cash flows from finance leases		7
Financing cash flows from finance leases		2
Operating		2
Progress Energy [Member]
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		60
Operating lease expense	40	82
Short-term lease expense	4	7
Variable lease expense	5	7
Finance lease expense
Amortization of leased assets	5	8
Interest on lease liabilities	13	19
Total finance lease expense	18	27
Total lease expense	67	123
Operating cash flows from finance leases		19
Financing cash flows from finance leases		8
Finance		175
Operating		30
Duke Energy Progress [Member]
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		23
Operating lease expense	17	36
Short-term lease expense	2	3
Variable lease expense	2	3
Finance lease expense
Amortization of leased assets	1	2
Interest on lease liabilities	10	14
Total finance lease expense	11	16
Total lease expense	32	58
Operating cash flows from finance leases		14
Financing cash flows from finance leases		2
Finance		175
Operating		30
Duke Energy Florida [Member]
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		37
Operating lease expense	23	46
Short-term lease expense	2	4
Variable lease expense	3	4
Finance lease expense
Amortization of leased assets	4	6
Interest on lease liabilities	3	5
Total finance lease expense	7	11
Total lease expense	35	65
Operating cash flows from finance leases		5
Financing cash flows from finance leases		6
Duke Energy Ohio [Member]
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		1
Operating lease expense	3	6
Short-term lease expense	1	1
Finance lease expense
Amortization of leased assets	1	1
Total finance lease expense	1	1
Total lease expense	5	8
Financing cash flows from finance leases		1
Duke Energy Indiana [Member]
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		3
Operating lease expense	5	10
Short-term lease expense		1
Finance lease expense
Interest on lease liabilities	1	1
Total finance lease expense	1	1
Total lease expense	6	12
Operating cash flows from finance leases		1
Piedmont Natural Gas [Member]
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases		5
Operating lease expense	2	3
Finance lease expense
Total lease expense	$ 2	3
Operating		$ 1