Summary of Significant Accounting Policies (New Accounting Standards) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Potential Increase (Decrease) in Restricted Cash	$ 147

The potential change in net cash inflow or outflow for the increase (decrease) associated with funds that are not available for withdrawal or use (such as funds held in escrow) and are associated with underlying transactions that are classified as investing activities.

No definition available.

Name:	duk_PotentialIncreaseDecreaseinRestrictedCash
Namespace Prefix:	duk_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant