Revenue (Unbilled Revenues) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 896	$ 944
Duke Energy Carolinas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	313	342
Progress Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	244	228
Duke Energy Progress [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	148	143
Duke Energy Florida [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	96	85
Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	2	4
Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	23	21
Piedmont Natural Gas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	73	86
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables		104
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables		$ 132
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	86
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 128