Goodwill and Intangibles Assets, net (Changes In Goodwill) (Details) $ in Millions	3 Months Ended
	Sep. 30, 2017 USD ($)
Goodwill [Roll Forward]
Balance at June 30, 2017	$ 1,741.0
Additions and other adjustments, net	0.0
Currency translation adjustments	16.3
Balance at September 30, 2017	1,757.3
Employer Services
Goodwill [Roll Forward]
Balance at June 30, 2017	1,736.2
Additions and other adjustments, net	0.0
Currency translation adjustments	16.3
Balance at September 30, 2017	1,752.5
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 September 30, 2017	$ 4.8