Fair Value Measurements (Reconciliation of Assets and Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs) (Details) - USD ($)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Transfers Between Activity Levels		$ 0	$ 0	$ 0
Investments
Beginning balance			5,000,000
Total pretax realized and unrealized gains included in comprehensive income			1,000,000
Sales			(6,000,000)
Ending balance	$ 5,000,000			5,000,000
Derivatives (net)
Beginning balance		(114,000,000)	(166,000,000)
Purchases		57,000,000	55,000,000
Settlements		(57,000,000)	(47,000,000)
Total gains (losses) included on the Consolidated Balance Sheet		1,000,000	44,000,000
Ending balance	(166,000,000)	(113,000,000)	(114,000,000)	(166,000,000)
Investments and Derivatives, Net
Beginning balance		(114,000,000)	(161,000,000)
Total pretax realized or unrealized gains included in other comprehensive income			1,000,000
Purchases			55,000,000
Sales			(6,000,000)
Settlements			(47,000,000)
Total gains (losses) included on the Consolidated Balance Sheet			44,000,000
Ending balance	(161,000,000)		(114,000,000)	(161,000,000)
Duke Energy Carolinas [Member]
Investments
Beginning balance			3,000,000
Total pretax realized and unrealized gains included in comprehensive income			1,000,000
Sales			(4,000,000)
Ending balance	3,000,000			3,000,000
Duke Energy Ohio [Member]
Derivatives (net)
Beginning balance		1,000,000	5,000,000
Purchases		7,000,000	3,000,000
Settlements		(4,000,000)	(4,000,000)
Total gains (losses) included on the Consolidated Balance Sheet		2,000,000	(3,000,000)
Ending balance	5,000,000	6,000,000	1,000,000	5,000,000
Duke Energy Indiana [Member]
Derivatives (net)
Beginning balance		27,000,000	16,000,000
Purchases		50,000,000	52,000,000
Settlements		(53,000,000)	(43,000,000)
Total gains (losses) included on the Consolidated Balance Sheet		(2,000,000)	2,000,000
Ending balance	16,000,000	22,000,000	27,000,000	16,000,000
Piedmont Natural Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Transfers Between Activity Levels	0				$ 0
Derivatives (net)
Beginning balance		(142,000,000)	(187,000,000)
Total gains (losses) and settlements		1,000,000	45,000,000
Ending balance	$ (187,000,000)	$ (141,000,000)	$ (142,000,000)	$ (187,000,000)