Goodwill And Intangible Assets, Net (Changes In Goodwill) (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Dec. 31, 2015	Jun. 30, 2015
Goodwill
Goodwill, Impairment Loss			$ 42.7
Goodwill [Roll Forward]
Balance at June 30, 2015 (A)		$ 1,793.5
Transfer of AMD goodwill (see Note 14)		0.0
Currency translation adjustments		(21.9)
Disposition of AMD		(100.4)
Balance at December 31, 2015		1,671.2	1,793.5
Employer Services [Member]
Goodwill [Roll Forward]
Balance at June 30, 2015 (A)	[1]	1,788.7
Transfer of AMD goodwill (see Note 14)		(100.4)
Currency translation adjustments		(21.9)
Disposition of AMD		0.0
Balance at December 31, 2015		1,666.4	1,788.7	[1]
PEO Services [Member]
Goodwill [Roll Forward]
Balance at June 30, 2015 (A)		4.8
Transfer of AMD goodwill (see Note 14)		0.0
Currency translation adjustments		0.0
Disposition of AMD		0.0
Balance at December 31, 2015		4.8	4.8
Other Segments [Member]
Goodwill [Roll Forward]
Balance at June 30, 2015 (A)		0.0
Transfer of AMD goodwill (see Note 14)		100.4
Currency translation adjustments		0.0
Disposition of AMD		(100.4)
Balance at December 31, 2015		$ 0.0	$ 0.0

[1] The goodwill balance at June 30, 2015 is net of accumulated impairment losses of $42.7 million related to the Employer Services segment.