Assets Held For Sale (Details) - USD ($)		1 Months Ended
	Sep. 30, 2015	Oct. 31, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and temporary cash investments	$ 2,000,000				$ 0
Total current assets	194,000,000			$ 0
Non-utility property, less accumulated depreciation of $13	572,000,000			388,000,000
Total current liabilities	82,000,000			$ 0
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and temporary cash investments	2,000,000
Accounts receivable	89,000,000
Accrued unbilled revenue	78,000,000
Other assets	3,000,000
Total current assets	172,000,000
Utility plant, less accumulated depreciation of $6	14,000,000
Non-utility property, less accumulated depreciation of $13	4,000,000
Regulatory assets	4,000,000
Total assets held for sale	194,000,000
Derivative liabilities	47,000,000
Accounts payable	6,000,000
Other	3,000,000
Total current liabilities	56,000,000
Derivative liabilities	22,000,000
Long-term debt	3,000,000
Other deferred credits and noncurrent liabilities	1,000,000
Total liabilities held for sale	82,000,000
Depreciation, utility plant	6,000,000
Depreciation, non-utility property	13,000,000
Impairment of long-lived assets to be disposed of			$ 0
Retail Electric Supply Business | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and temporary cash investments	0
Accounts receivable	89,000,000
Accrued unbilled revenue	78,000,000
Other assets	2,000,000
Total current assets	169,000,000
Utility plant, less accumulated depreciation of $6	0
Non-utility property, less accumulated depreciation of $13	4,000,000
Regulatory assets	0
Total assets held for sale	173,000,000
Derivative liabilities	47,000,000
Accounts payable	6,000,000
Other	2,000,000
Total current liabilities	55,000,000
Derivative liabilities	22,000,000
Long-term debt	0
Other deferred credits and noncurrent liabilities	0
Total liabilities held for sale	77,000,000
Pike | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and temporary cash investments	2,000,000
Accounts receivable	0
Accrued unbilled revenue	0
Other assets	1,000,000
Total current assets	3,000,000
Utility plant, less accumulated depreciation of $6	14,000,000
Non-utility property, less accumulated depreciation of $13	0
Regulatory assets	4,000,000
Total assets held for sale	21,000,000
Derivative liabilities	0
Accounts payable	0
Other	1,000,000
Total current liabilities	1,000,000
Derivative liabilities	0
Long-term debt	3,000,000
Other deferred credits and noncurrent liabilities	1,000,000
Total liabilities held for sale	5,000,000
Impairment of long-lived assets to be disposed of	5,000,000
Impairment of long-lived assets to be disposed of, net of taxes	$ 3,000,000
Subsequent Event | Pike | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of business		$ 16,000,000