Financial Data By Segment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended												12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	[1]	Mar. 31, 2019	[1]	Dec. 31, 2018	[1]	Sep. 30, 2018	[1]	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
TOTAL REVENUES	$ 3,376.8	$ 4,047.8	$ 3,669.5	$ 3,495.7	$ 3,479.3		$ 3,828.2		$ 3,492.4		$ 3,310.3		$ 14,589.8	$ 14,110.2	$ 13,274.2
Restatement Adjustment [Member]
Segment Reporting Information [Line Items]
TOTAL REVENUES														(65.0)	(53.5)
United States [Member]
Segment Reporting Information [Line Items]
TOTAL REVENUES													$ 12,740.1	$ 12,262.6	$ 11,439.8

[1] (A) The prior period amounts presented have been revised to correct the amounts previously reported on a gross basis to a net basis by reducing PEO revenues and operating expenses for associated costs of an equal amount of $12.9 million, $13.5 million, $19.2 million and $19.4 million for the first quarter, second quarter, third quarter and fourth quarter, respectively. Refer to Note 1 to our consolidated financial statements for more information on this revision.