Debt and Credit Facilities (Details) - Debt-to-Capitalization Ratios	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
AGL Resources Inc [Member]
Schedule of Capitalization [Line Items]
Debt covenants (as a percent	0.52	0.55	0.53
Nicor Gas [Member]
Schedule of Capitalization [Line Items]
Debt covenants (as a percent	0.56	0.62	0.57

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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