Cover Page - USD ($)	12 Months Ended
	Jun. 30, 2019	Jul. 31, 2019	Dec. 31, 2018
Cover page.
Document Type	10-K
Entity Public Float			$ 56,967,135,372
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Entity Registrant Name	AUTOMATIC DATA PROCESSING INC
Entity Central Index Key	0000008670
Current Fiscal Year End Date	--06-30
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		433,942,837