Joint Ownership Agreements (Tables)

9 Months Ended

Sep. 30, 2017

Regulated Operations [Abstract]

Equity Method Investments

The carrying amounts of Southern Company Gas' equity method investments as of September 30, 2017 and December 31, 2016 and related income from those investments for the successor three and nine month periods ended September 30, 2017, the successor three-month period ended September 30, 2016, and for the predecessor period January 1, 2016 through June 30, 2016 were as follows:

Balance Sheet Information	September 30, 2017		December 31, 2016
	(in millions)
SNG	$	1,385	$	1,394
Atlantic Coast Pipeline	61		33
PennEast Pipeline	49		22
Triton	43		44
Pivotal JAX LNG, LLC	40		16
Horizon Pipeline	30		30
Other	1		2
Total	$	1,609	$	1,541

Selected financial information of SNG for the three and nine months ended September 30, 2017 and for the period September 1, 2016 through September 30, 2016 is as follows:

Income Statement Information	Three Months Ended September 30, 2017		Nine Months Ended September 30, 2017		September 1, 2016 through September 30, 2016
	(in millions)
Revenues	$	146	$	445	$	82
Operating income	$	71	$	218	$	60
Net income	$	57	$	172	$	55

Schedule of Other Nonoperating Income, by Component

	Successor		Successor		Successor		Predecessor
Income Statement Information	Three Months Ended September 30, 2017		Three Months Ended September 30, 2016		Nine Months Ended September 30, 2017		January 1, 2016 through June 30, 2016
	(in millions)		(in millions)		(in millions)		(in millions)
SNG	$	28	$	27	$	86	$	—
PennEast Pipeline	1		—		5		—
Atlantic Coast Pipeline	1		1		4		—
Triton	1		1		3		1
Horizon Pipeline	1		—		2		1
Total	$	32	$	29	$	100	$	2