Debt and Credit Facilities - Debt-to-Capitalization Ratios (Details)	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Southern Gas [Member]
Schedule of Capitalization [Line Items]
Debt covenants (as a percent)	0.52	0.54	0.49
Nicor Gas [Member]
Schedule of Capitalization [Line Items]
Debt covenants (as a percent)	0.45	0.56	0.49

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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