Investments in Debt and Equity Securities (Available-For-Sale Investments) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			$ 2,899
Gross Unrealized Holding Losses			42
Estimated Fair Value			7,451
Realized Gains	$ 37	$ 170
Realized Losses	25	124
Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2,837
Gross Unrealized Holding Losses			40
Estimated Fair Value			7,088
Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			115
Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2,805
Gross Unrealized Holding Losses			27
Estimated Fair Value			4,914
Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			17
Gross Unrealized Holding Losses			2
Estimated Fair Value			570
Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			4
Gross Unrealized Holding Losses			3
Estimated Fair Value			344
Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			11
Gross Unrealized Holding Losses			7
Estimated Fair Value			1,027
Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			118
Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			62
Gross Unrealized Holding Losses			2
Estimated Fair Value			363
Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			15
Other Classification [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			59
Estimated Fair Value			123
Other Classification [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1
Estimated Fair Value			57
Other Classification [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Gross Unrealized Holding Losses			1
Estimated Fair Value			83
Other Classification [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			41
Other Classification [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			44
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale [Line Items]
Realized Gains	20	110
Realized Losses	13	76
Duke Energy Carolinas [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,543
Gross Unrealized Holding Losses			20
Estimated Fair Value			3,758
Duke Energy Carolinas [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			32
Duke Energy Carolinas [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,531
Gross Unrealized Holding Losses			12
Estimated Fair Value			2,692
Duke Energy Carolinas [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			9
Gross Unrealized Holding Losses			2
Estimated Fair Value			359
Duke Energy Carolinas [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			60
Duke Energy Carolinas [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			3
Gross Unrealized Holding Losses			4
Estimated Fair Value			503
Duke Energy Carolinas [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			112
Progress Energy [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,296
Gross Unrealized Holding Losses			20
Estimated Fair Value			3,389
Realized Gains	16	58
Realized Losses	12	47
Progress Energy [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,294
Gross Unrealized Holding Losses			20
Estimated Fair Value			3,330
Progress Energy [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			83
Progress Energy [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,274
Gross Unrealized Holding Losses			15
Estimated Fair Value			2,222
Progress Energy [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			8
Estimated Fair Value			211
Progress Energy [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			4
Gross Unrealized Holding Losses			2
Estimated Fair Value			284
Progress Energy [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			8
Gross Unrealized Holding Losses			3
Estimated Fair Value			524
Progress Energy [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			6
Progress Energy [Member] | Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			59
Progress Energy [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			12
Progress Energy [Member] | Other Classification [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			47
Duke Energy Progress [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			995
Gross Unrealized Holding Losses			16
Estimated Fair Value			2,592
Realized Gains	14	49
Realized Losses	11	41
Duke Energy Progress [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			995
Gross Unrealized Holding Losses			16
Estimated Fair Value			2,591
Duke Energy Progress [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			50
Duke Energy Progress [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			980
Gross Unrealized Holding Losses			12
Estimated Fair Value			1,795
Duke Energy Progress [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			6
Estimated Fair Value			149
Duke Energy Progress [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			4
Gross Unrealized Holding Losses			2
Estimated Fair Value			283
Duke Energy Progress [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			5
Gross Unrealized Holding Losses			2
Estimated Fair Value			310
Duke Energy Progress [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			4
Duke Energy Progress [Member] | Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Progress [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Florida [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			301
Gross Unrealized Holding Losses			4
Estimated Fair Value			787
Realized Gains	2	9
Realized Losses	$ 1	$ 6
Duke Energy Florida [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			299
Gross Unrealized Holding Losses			4
Estimated Fair Value			739
Duke Energy Florida [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			33
Duke Energy Florida [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			294
Gross Unrealized Holding Losses			3
Estimated Fair Value			427
Duke Energy Florida [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			62
Duke Energy Florida [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Florida [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			3
Gross Unrealized Holding Losses			1
Estimated Fair Value			214
Duke Energy Florida [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			2
Duke Energy Florida [Member] | Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			48
Duke Energy Florida [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Florida [Member] | Other Classification [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			47
Duke Energy Indiana [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			49
Gross Unrealized Holding Losses			1
Estimated Fair Value			128
Duke Energy Indiana [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			49
Estimated Fair Value			97
Duke Energy Indiana [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			3
Duke Energy Indiana [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			$ 28