Consolidated Statements of Equity - Indiana (USD $) In Millions	Total	Retained Earnings [Member]	Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Duke Energy Indiana [Member]	Duke Energy Indiana [Member] Common Stock [Member]	Duke Energy Indiana [Member] Additional Paid In Capital [Member]	Duke Energy Indiana [Member] Retained Earnings [Member]	Duke Energy Indiana [Member] Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]
Balance at Dec. 31, 2009					$ 2,934	$ 1	$ 1,008	$ 1,915	$ 10
Net income	1,323	1,320			285			285
Other comprehensive income (loss), net of tax	373		4	276	(2)				(2)
Transfer of Vermillion Generating Station					0
Contributions from parent					350		350
Balance at Dec. 31, 2010					3,567	1	1,358	2,200	8
Net income	513				76
Balance at Mar. 31, 2011
Balance at Dec. 31, 2010					3,567	1		2,200	8
Net income	1,714	1,706			168			168
Other comprehensive income (loss), net of tax	(243)		(53)	(49)	(1)				(1)
Transfer of Vermillion Generating Station					0
Contributions from parent					0
Balance at Dec. 31, 2011	22,772				3,734	1		2,368	7
Balance at Sep. 30, 2011
Net income	290				55
Balance at Dec. 31, 2011	22,772				3,734	1
Net income	299				(167)
Balance at Mar. 31, 2012
Balance at Dec. 31, 2011	22,772				3,734	1	1,358	2,368	7
Net income	1,782	1,768			(50)			(50)
Other comprehensive income (loss), net of tax	(76)		(29)	19	(2)				(2)
Transfer of Vermillion Generating Station					26		26
Contributions from parent					0
Balance at Dec. 31, 2012	40,863				3,708	1	1,384	2,318	5
Balance at Sep. 30, 2012
Net income	437				59
Balance at Dec. 31, 2012	$ 40,863				$ 3,708	$ 1