Document And Entity Information - shares	6 Months Ended
	Dec. 31, 2018	Jan. 25, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Entity Registrant Name	AUTOMATIC DATA PROCESSING INC
Entity Central Index Key	0000008670
Current Fiscal Year End Date	--06-30
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Common Stock, Shares Outstanding		435,629,656