Proposed Merger (Details) - USD ($)			6 Months Ended
	Apr. 01, 2019	Mar. 31, 2019	Sep. 30, 2019	Mar. 31, 2019
Merger Sub
Business Acquisition [Line Items]
Termination fee payable to parent	$ 20,000,000
Expense reimbursement amount to parent, maximum	5,000,000
Expense reimbursement amount from parent, maximum	$ 5,000,000
Subsequent Event | Merger Sub
Business Acquisition [Line Items]
Dividends declared per common share (in USD per share, no less than)	$ 0.95
Subsequent Event | Forecast | Merger Sub
Business Acquisition [Line Items]
Proposed consideration			$ 530,000,000
Subsequent Event | Common Stock | Forecast | Merger Sub
Business Acquisition [Line Items]
Proposed consideration issuable (in shares)			34,600,000
Units issuable (in units)			10,615,711
Subsequent Event | Common Stock | Proposed Consideration One | Forecast | Merger Sub
Business Acquisition [Line Items]
Number of shares issuable per acquiree stock (in shares)			0.6378
Subsequent Event | Common Stock | Proposed Consideration Two | Forecast | Merger Sub
Business Acquisition [Line Items]
Number of shares issuable per acquiree stock (in shares)			0.500
Subsequent Event | Cash Without Interest | Proposed Consideration Two | Forecast | Merger Sub
Business Acquisition [Line Items]
Cash issuable per acquiree stock			$ 7.63
Subsequent Event | Cash Without Interest | Proposed Consideration Three | Forecast | Merger Sub
Business Acquisition [Line Items]
Cash issuable per acquiree stock			$ 35.325
AmeriGas Propane | AmeriGas Partners
Business Acquisition [Line Items]
General Partner held a general partner interest in AmeriGas Partners (percentage)		1.00%		1.00%