Revenue (Unbilled Revenues) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 790	$ 896
Duke Energy Carolinas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	288	313
Progress Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	270	244
Duke Energy Progress [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	148	148
Duke Energy Florida [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	122	96
Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	1	2
Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	14	23
Piedmont Natural Gas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	4	73
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	65	86
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 116	$ 128