Asset Retirement Obligations (ARO Rollforward) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	$ 8,466
Acquisitions	213
Accretion expense	278
Liabilities settled	(274)
Liabilities incurred in the current year	983
Revision in estimates of cash flows	47
Balance at end of period	9,713
Duke Energy Carolinas [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	3,428
Accretion expense	123
Liabilities settled	(107)
Liabilities incurred in the current year	178
Revision in estimates of cash flows	(23)
Balance at end of period	3,599
Progress Energy [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	4,711
Acquisitions	204
Accretion expense	150
Liabilities settled	(153)
Liabilities incurred in the current year	270
Revision in estimates of cash flows	40
Balance at end of period	5,222
Duke Energy Progress [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	3,905
Acquisitions	204
Accretion expense	123
Liabilities settled	(53)
Liabilities incurred in the current year	270
Revision in estimates of cash flows	40
Balance at end of period	4,489
Duke Energy Florida [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	806
Accretion expense	26
Liabilities settled	(100)
Balance at end of period	732
Duke Energy Ohio [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	27
Accretion expense	2
Liabilities settled	(2)
Liabilities incurred in the current year	116
Balance at end of period	143
Duke Energy Indiana [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	32
Accretion expense	11
Liabilities settled	(12)
Liabilities incurred in the current year	418
Balance at end of period	$ 449