Goodwill and Intangibles Assets, net (Changes In Goodwill) (Details) $ in Millions	6 Months Ended
	Dec. 31, 2018 USD ($)
Goodwill [Roll Forward]
Balance at June 30, 2018	$ 2,243.5
Additions and other adjustments	90.9
Currency translation adjustments	(13.0)
Balance at December 31, 2018	2,321.4
Employer Services
Goodwill [Roll Forward]
Balance at June 30, 2018	2,238.7
Additions and other adjustments	90.9
Currency translation adjustments	(13.0)
Balance at December 31, 2018	2,316.6
PEO Services
Goodwill [Roll Forward]
Balance at June 30, 2018	4.8
Additions and other adjustments	0.0
Currency translation adjustments	0.0
Balance at December 31, 2018	$ 4.8