Partnership Organization and Formation - Additional Information (Details) - shares	Jun. 30, 2018	Sep. 30, 2017
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Common units outstanding (in units)	61,405,409	61,105,000
Ownership interest in Suburban Energy Finance Corp (in hundredths)	100.00%
General Partner [Member] | Common Unitholders [Member]
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Common units outstanding (in units)	784