New Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Reclassification from AOCI to retained earnings, tax effect	$ (42.3)	$ 42.3
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net decrease / (increase) in restricted cash and cash equivalents held to satisfy client funds obligations			$ 0.0
Net cash flows used in investing activities		(1,958.0)	(954.7)
Effect of exchange rate changes on cash, cash equivalents, restricted cash, and restricted cash equivalents			(81.1)
Net change in cash, cash equivalents, restricted cash, and restricted cash equivalents			(353.6)
Cash, cash equivalents, restricted cash, and restricted cash equivalents, end of period	$ 13,444.9	$ 13,444.9	15,105.0	$ 8,181.6
Accounting Standards Update 2016-18 | As previously reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net decrease / (increase) in restricted cash and cash equivalents held to satisfy client funds obligations			87.7
Net cash flows used in investing activities			(867.0)
Effect of exchange rate changes on cash, cash equivalents, restricted cash, and restricted cash equivalents			(10.8)
Net change in cash, cash equivalents, restricted cash, and restricted cash equivalents			(195.6)
Cash, cash equivalents, restricted cash, and restricted cash equivalents, end of period			2,995.5
Accounting Standards Update 2016-18 | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net decrease / (increase) in restricted cash and cash equivalents held to satisfy client funds obligations			(87.7)
Net cash flows used in investing activities			(87.7)
Effect of exchange rate changes on cash, cash equivalents, restricted cash, and restricted cash equivalents			(70.3)
Net change in cash, cash equivalents, restricted cash, and restricted cash equivalents			(158.0)
Cash, cash equivalents, restricted cash, and restricted cash equivalents, end of period			$ 12,109.5