Assets Held For Sale (Details) - USD ($)		1 Months Ended		3 Months Ended
	Sep. 30, 2015	Oct. 31, 2015	Jun. 30, 2015	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
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				166,000,000	$ 157,000,000
Non-utility property, less accumulated depreciation of $13				859,000,000	832,000,000
Total current liabilities				150,000,000	$ 89,000,000
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of long-lived assets to be disposed of			$ 0
Cash and temporary cash investments				7,000,000
Accounts receivable less allowance for uncollectible accounts of $2				67,000,000
Accrued unbilled revenue				68,000,000
Other assets				3,000,000
Total current assets				145,000,000
Utility plant, less accumulated depreciation of $6				14,000,000
Non-utility property, less accumulated depreciation of $13				3,000,000
Non-utility property construction work in progress				1,000,000
Regulatory assets				3,000,000
Total assets held for sale				166,000,000
Fair value of derivative liabilities				98,000,000
Accounts payable				3,000,000
Other				5,000,000
Total current liabilities				106,000,000
Fair value of derivative liabilities				41,000,000
Long-term debt				3,000,000
Total liabilities held for sale				150,000,000
Allowance for uncollectible accounts				2,000,000
Depreciation, utility plant				6,000,000
Depreciation, non-utility property				13,000,000
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 less allowance for uncollectible accounts of $2				67,000,000
Accrued unbilled revenue				67,000,000
Other assets				2,000,000
Total current assets				136,000,000
Utility plant, less accumulated depreciation of $6				0
Non-utility property, less accumulated depreciation of $13				3,000,000
Non-utility property construction work in progress				1,000,000
Regulatory assets				0
Total assets held for sale				140,000,000
Fair value of derivative liabilities				98,000,000
Accounts payable				3,000,000
Other				3,000,000
Total current liabilities				104,000,000
Fair value of derivative liabilities				41,000,000
Long-term debt				0
Total liabilities held for sale				145,000,000
Pike | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of long-lived assets to be disposed of	$ 5,000,000
Proceeds from divestiture of business		$ 16,000,000
Impairment of long-lived assets to be disposed of, net of taxes	$ 3,000,000
Cash and temporary cash investments				7,000,000
Accounts receivable less allowance for uncollectible accounts of $2				0
Accrued unbilled revenue				1,000,000
Other assets				1,000,000
Total current assets				9,000,000
Utility plant, less accumulated depreciation of $6				14,000,000
Non-utility property, less accumulated depreciation of $13				0
Non-utility property construction work in progress				0
Regulatory assets				3,000,000
Total assets held for sale				26,000,000
Fair value of derivative liabilities				0
Accounts payable				0
Other				2,000,000
Total current liabilities				2,000,000
Fair value of derivative liabilities				0
Long-term debt				3,000,000
Total liabilities held for sale				$ 5,000,000