Goodwill and Intangibles Assets, net - Changes In Goodwill (Details) $ in Millions	6 Months Ended
	Dec. 31, 2020 USD ($)
Goodwill [Roll Forward]
Balance at June 30, 2020	$ 2,309.4
Additions and other adjustments	0.0
Currency translation adjustments	37.2
Balance at December 31, 2020	2,346.6
Employer Services
Goodwill [Roll Forward]
Balance at June 30, 2020	2,304.6
Additions and other adjustments	0.0
Currency translation adjustments	37.2
Balance at December 31, 2020	2,341.8
PEO Services
Goodwill [Roll Forward]
Balance at June 30, 2020	4.8
Additions and other adjustments	0.0
Currency translation adjustments	0.0
Balance at December 31, 2020	$ 4.8