Acquisitions and Dispositions - Acquisitions (Narrative) (Details) shares in Millions, $ in Millions		3 Months Ended								9 Months Ended	12 Months Ended
	Oct. 03, 2016 USD ($)	Dec. 31, 2016 USD ($) shares	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2015 USD ($) MW	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 31, 2016 shares	Aug. 31, 2016 USD ($)	Aug. 01, 2016 USD ($)
Business Acquisition [Line Items]
Net Income (Loss) Attributable to Parent		$ (227)	$ 1,176	$ 509	$ 694	$ 477	$ 932	$ 543	$ 864		$ 2,152	$ 2,816	$ 1,883
Long-term Debt		$ 47,895				38,868					47,895	38,868
Asset retirement obligations assumed											22	226
Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 5,000
Long-term debt assumed	$ 2,002
Business Combination, Integration Related Costs											439	9
Business Combination, After Tax Integration Related Costs											279	19
Revenues											367
Net Income (Loss) Attributable to Parent											$ 20
Long-term Debt															$ 3,750
Bridge Facility																$ 4,900
Forward Contract Indexed to Issuer's Equity, Indexed Shares | shares		10.6									10.6			10.6
Proceeds from Issuance or Sale of Equity											$ 723
Duke Energy Progress [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross												1,249
Net Income (Loss) Attributable to Parent		$ 60	271	$ 131	$ 137	69	229	$ 85	$ 183		599	566	$ 467
Long-term Debt		7,011				$ 6,518					7,011	6,518
Asset retirement obligations assumed												$ 204
Duke Energy Progress [Member] | NCEMPA Generating Assets [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross										$ 1,250
Owned Plant Capacity | MW										700
Acquisition adjustment, recorded within property, plant and equipment							350			$ 350
Nuclear decommissioning trust fund assets transferred							$ 287			287
Asset retirement obligations assumed										$ 204
Interest Rate Contract [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments											190
Sales [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											10
Operating Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											101
Operating Income (Loss) [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											46
Interest Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											234
August 2016 Term Loan Facility [Member]
Business Acquisition [Line Items]
Long-term Line of Credit		750									750
Bridge Facility																$ 1,500
August 2016 Term Loan Facility [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Long-term Line of Credit		$ 750	750								750
Bridge Facility			$ 1,500
Other Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											104
Other Expense [Member] | Operating Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											94
Other Expense [Member] | Operating Income (Loss) [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											$ 10