Employee Benefit Plans (Fair Value Measurements of Plan Assets - Master Retirement Trust) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 8,618	$ 8,261
Master Trust [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	1,816	2,120
Master Trust [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	6,366	5,595
Master Trust [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	436	546
Master Trust [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	2,346	2,877
Master Trust [Member] | Equity Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	1,625	1,801
Master Trust [Member] | Equity Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	721	1,022
Master Trust [Member] | Equity Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		54
Master Trust [Member] | Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	4,349	2,604
Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	4,348	2,601
Master Trust [Member] | Corporate Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	1	3
Master Trust [Member] | Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	333	1,158
Master Trust [Member] | Short Term Investments [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	171	254
Master Trust [Member] | Short Term Investments [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	162	904
Master Trust [Member] | Partnership Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	298	307
Master Trust [Member] | Partnership Interest [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	298	307
Master Trust [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	146	164
Master Trust [Member] | Hedge Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	146	111
Master Trust [Member] | Hedge Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		53
Master Trust [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	104	95
Master Trust [Member] | Real Estate [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	104	95
Master Trust [Member] | US Treasury and Government [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	917	927
Master Trust [Member] | US Treasury and Government [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	916	927
Master Trust [Member] | US Treasury and Government [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	1
Master Trust [Member] | Guaranteed Investment Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	32	33
Master Trust [Member] | Guaranteed Investment Contracts [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	32	33
Master Trust [Member] | Government Bonds - Foreign [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	44	19
Master Trust [Member] | Government Bonds - Foreign [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	44	18
Master Trust [Member] | Government Bonds - Foreign [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		1
Master Trust [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	30	58
Master Trust [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	30	58
Master Trust [Member] | Asset Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	9	7
Master Trust [Member] | Asset Backed Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	9	7
Master Trust [Member] | Miscellaneous Investments And Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	10	12
Master Trust [Member] | Miscellaneous Investments And Other [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	(10)	7
Master Trust [Member] | Miscellaneous Investments And Other [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	20	5
VEBA I [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	48	51
VEBA I [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	48	51
VEBA I [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	14	15
VEBA I [Member] | Equity Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	14	15
VEBA I [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	21	21
VEBA I [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	21	21
VEBA I [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	13	15
VEBA I [Member] | Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 13	$ 15
Duke Energy Carolinas [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	28.00%	28.00%
Progress Energy [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	31.00%	35.00%
Duke Energy Progress [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	15.00%	16.00%
Duke Energy Florida [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	16.00%	16.00%
Duke Energy Ohio [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	5.00%	5.00%
Duke Energy Indiana [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	8.00%	8.00%