Summary of Significant Accounting Policies - Allocation of Net Income (Loss) (Details)	3 Months Ended
Dec. 31, 2017
AmeriGas Propane Inc Partnership Interest in AmeriGas Partners
Investment
General partners ownership interest (as a percent)	1.00%

Percentage investment held by the managing member or general partner of the limited liability company (LLC) or limited partnership (LP).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration