Discontinued Operations - Components of Discontinued Operations (Details) - Predecessor [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended	12 Months Ended
	Sep. 30, 2014	Mar. 31, 2014	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Tropical Shipping [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues					$ 243
Cost of goods sold					149
Operation and maintenance					75
Depreciation and amortization					5
Taxes other than income taxes					5
Loss on sale and goodwill impairment					28
Total operating expenses					262
Operating (loss) income					(19)
(Loss) income before income taxes					(19)
Income tax expense					(61)
(Loss) income from discontinued operations, net of tax					(80)
Southern Company Gas [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense	$ (29)	$ (31)			(60)
(Loss) income from discontinued operations, net of tax			$ 0	$ 0	(80)
Depreciation and monetary suspension					7
Goodwill impairment					$ 19