Goodwill and Intangibles Assets, net (Changes In Goodwill) (Details) $ in Millions	9 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Balance at June 30, 2017	$ 1,741.0
Additions and other adjustments, net	491.3
Currency translation adjustments	31.0
Balance at March 31, 2018	2,263.3
Employer Services
Goodwill [Roll Forward]
Balance at June 30, 2017	1,736.2
Additions and other adjustments, net	491.3
Currency translation adjustments	31.0
Balance at March 31, 2018	2,258.5
PEO Services
Goodwill [Roll Forward]
Balance at June 30, 2017	4.8
Additions and other adjustments, net	0.0
Currency translation adjustments	0.0
Balance at March 31, 2018	$ 4.8