Related Party Transactions Related Party Transactions (Intercompany Income Taxes) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Duke Energy Carolinas [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	$ 74	$ 107
Due to Related Parties, Current	250	229
Duke Energy Carolinas [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current		122
Due to Related Parties, Current	6
Progress Energy [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	37	375
Due to Related Parties, Current	256	311
Progress Energy [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	170	120
Duke Energy Progress [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	6	16
Due to Related Parties, Current	176	190
Duke Energy Progress [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	22	104
Duke Energy Florida [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	27	84
Due to Related Parties, Current	76	116
Duke Energy Florida [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	16
Due to Related Parties, Current		96
Duke Energy Ohio [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	93	84
Due to Related Parties, Current	53	53
Duke Energy Ohio [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current		54
Due to Related Parties, Current	9
Duke Energy Indiana [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	64	71
Due to Related Parties, Current	61	83
Duke Energy Indiana [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due to Related Parties, Current	$ 60	$ 47