Commitments and Contingencies - Contingencies (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2017 USD ($) subsidiary	Sep. 30, 2016 USD ($)
CPG; PNG and UGI Gas COAs
Contingencies
Accrued liabilities for environmental investigation and remediation costs	$ 54,250	$ 55,063
Environmental Issue | UGI Utilities
Contingencies
Environmental expenditures cap during calendar year	2,500
Environmental Issue | CPG MGP
Contingencies
Environmental expenditures cap during calendar year	1,750
Environmental Issue | PNG MGP
Contingencies
Environmental expenditures cap during calendar year	$ 1,100
PNG and CPG
Contingencies
Number of subsidiaries acquired with similar histories | subsidiary	2