Document And Entity Information - shares	9 Months Ended
	Apr. 30, 2018	May 31, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	DONALDSON CO INC
Entity Central Index Key	0000029644
Current Fiscal Year End Date	--07-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Apr. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		128,977,999