Document And Entity Information - shares	6 Months Ended
	Mar. 31, 2019	Sep. 30, 2018
Document Information [Line Items]
Capital Units, Outstanding	13,327	13,327
Entity Registrant Name	SOUTHWEST IOWA RENEWABLE ENERGY, LLC
Entity Central Index Key	0001424844
Current Fiscal Year End Date	--09-30
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Document Type	10-Q
Entity Emerging Growth Company	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Capital Unit, Class A [Member]
Document Information [Line Items]
Capital Units, Outstanding	8,993
Capital Unit, Class B [Member]
Document Information [Line Items]
Capital Units, Outstanding	3,334
Capital Unit Class C [Member]
Document Information [Line Items]
Capital Units, Outstanding	1,000
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	8,993
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	3,334
Common Class C [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	1,000