Document And Entity Information In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Nov. 01, 2012
Document Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Entity Registrant Name	Southern Union Co
Entity Central Index Key	0000203248
Document Period End Date	Sep. 30, 2012
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		0
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes