Related Party Transactions (Pension)(Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Duke Energy Carolinas [Member]
Other current liabilities	$ 8	$ 8
Accrued pension and other post-retirement benefit costs	232	248
Total allocated accrued pension and other post-retirement benefit obligations	240	256
Duke Energy Ohio [Member]
Other current liabilities	4	4
Accrued pension and other post-retirement benefit costs	160	166
Total allocated accrued pension and other post-retirement benefit obligations	164	170
Duke Energy Indiana [Member]
Other current liabilities	2	2
Accrued pension and other post-retirement benefit costs	222	231
Total allocated accrued pension and other post-retirement benefit obligations	$ 224	$ 233