Supplemental Financial Statement Information (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jul. 31, 2012 gal	Jul. 31, 2011	Jul. 31, 2010
Supplemental Financial Statement Information [Line Items]
Net procurement of fixed priced propane by Ferrellgas in gallons	104,800,000
Depreciation	$ 60.0	$ 58.7	$ 61.3
Ferrellgas, L.P. [Member]
Supplemental Financial Statement Information [Line Items]
Net procurement of fixed priced propane by Ferrellgas in gallons	104,800,000
Depreciation	$ 60.0	$ 58.7	$ 61.3
Maximum [Member]
Supplemental Financial Statement Information [Line Items]
Contract term duration	1 year
Supply procurement contract duration	36 months
Maximum [Member] | Ferrellgas, L.P. [Member]
Supplemental Financial Statement Information [Line Items]
Contract term duration	1 year
Supply procurement contract duration	36 months