Related Party Transactions Related Party Transactions (Intercompany Income Taxes) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Duke Energy Carolinas [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	$ 71	$ 107
Due to Related Parties, Current	173	229
Duke Energy Carolinas [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	10	122
Progress Energy [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	11	375
Due to Related Parties, Current	232	311
Progress Energy [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	90	120
Duke Energy Progress [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	9	16
Due to Related Parties, Current	134	190
Duke Energy Progress [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current		104
Due to Related Parties, Current	11
Duke Energy Florida [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	3	84
Due to Related Parties, Current	100	116
Duke Energy Florida [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due to Related Parties, Current	48	96
Duke Energy Ohio [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	35	84
Due to Related Parties, Current	76	53
Duke Energy Ohio [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	15	54
Duke Energy Indiana [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	60	71
Due to Related Parties, Current	87	83
Duke Energy Indiana [Member] | Income Taxes [Member]
Income Tax Disclosure [Line Items]
Due from Related Parties, Current	$ 6
Due to Related Parties, Current		$ 47