Notes Receivable (Schedule Of Current And Non-Current Notes Receivable) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	$ 128	$ 98
EnerBank notes receivable held for sale	16	41
Total notes receivable	1,161	939
EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	144	138
Noncurrent notes receivable	1,017	800
Receivables, Net Of Allowance For Loan Losses [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	128	97
Receivables Held For Sale [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	$ 16	41
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable		$ 1