Joint Ownership Agreements (Tables)

3 Months Ended

Mar. 31, 2018

Regulated Operations [Abstract]

Equity Method Investments

The carrying amounts of Southern Company Gas' equity method investments as of March 31, 2018 and December 31, 2017 and related income from those investments for the three-month periods ended March 31, 2018 and March 31, 2017 were as follows:

Balance Sheet Information	March 31, 2018		December 31, 2017
	(in millions)
SNG	$	1,274	$	1,262
Atlantic Coast Pipeline	49		41
PennEast Pipeline	62		57
Triton	42		42
Pivotal JAX LNG, LLC	45		44
Horizon Pipeline	31		30
Other	1		1
Total	$	1,504	$	1,477

Selected financial information of SNG for the three months ended March 31, 2018 and March 31, 2017 is as follows:

Income Statement Information	Three Months Ended March 31, 2018		Three Months Ended March 31, 2017
	(in millions)
Revenues	$	160	$	155
Operating income	$	99	$	84
Net income	$	78	$	66

Schedule of Other Nonoperating Income, by Component

Income Statement Information	Three Months Ended March 31, 2018		Three Months Ended March 31, 2017
	(in millions)
SNG	$	39	$	34
PennEast Pipeline	1		3
Atlantic Coast Pipeline	1		1
Triton	1		—
Horizon Pipeline	—		1
Total	$	42	$	39