Summary of Significant Accounting Policies (Inventory)(Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Public Utilities, Inventory [Line Items]
Materials and supplies	$ 2,374	$ 2,343
Coal	774	1,105
Natural gas, oil, other	374	298
Total inventory	3,522	3,746
Duke Energy Carolinas [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	767	785
Coal	251	451
Natural gas, oil, other	37	40
Total inventory	1,055	1,276
Progress Energy [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	1,167	1,133
Coal	314	370
Natural gas, oil, other	236	248
Total inventory	1,717	1,751
Duke Energy Progress [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	813	776
Coal	148	192
Natural gas, oil, other	115	120
Total inventory	1,076	1,088
Duke Energy Florida [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	354	357
Coal	166	178
Natural gas, oil, other	121	128
Total inventory	641	663
Duke Energy Ohio [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	84	81
Coal	19	16
Natural gas, oil, other	34	8
Total inventory	137	105
Duke Energy Indiana [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	312	301
Coal	190	267
Natural gas, oil, other	2	2
Total inventory	$ 504	$ 570