Related Party Transactions Related Party Transactions (Intercompany Income Taxes) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Duke Energy Carolinas [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	$ 88	$ 107
Due to Related Parties, Current	149	229
Duke Energy Carolinas [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current		122
Due to Related Parties, Current	64
Progress Energy [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	8	375
Due to Related Parties, Current	202	311
Progress Energy [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	113	120
Duke Energy Progress [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	5	16
Due to Related Parties, Current	143	190
Duke Energy Progress [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	56	104
Duke Energy Florida [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	5	84
Due to Related Parties, Current	61	116
Duke Energy Florida [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due to Related Parties, Current	65	96
Duke Energy Ohio [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	96	84
Due to Related Parties, Current	49	53
Duke Energy Ohio [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current		54
Due to Related Parties, Current	27
Duke Energy Indiana [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	74	71
Due to Related Parties, Current	82	83
Duke Energy Indiana [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	$ 67
Due to Related Parties, Current		$ 47