Subsequent Event (Details) (Alabama Gas Corporation, Subsequent Event, USD $)	1 Months Ended
Apr. 30, 2014
Alabama Gas Corporation \| Subsequent Event
Subsequent Event [Line Items]
Expected amount of consideration to be received	$ 1,600,000,000
Expected proceeds from sale of Alagasco	1,280,000,000
Expected amount of debt to be assigned	$ 320,000,000

Noncash or Part Noncash Divestiture, Expected Amount of Consideration to be Received

No definition available.

Name:	egn_NoncashorPartNoncashDivestitureExpectedAmountofConsiderationtobeReceived
Namespace Prefix:	egn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration