Statements of Consolidated Earnings (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Direct Pass Through Costs P E O Revenues		$ 10,632.3	$ 9,145.5	$ 19,370.8	$ 16,833.1
REVENUES:
Revenues, other than interest on funds held for clients and PEO revenues		2,188.8	2,077.4	4,269.8	4,114.8
Interest on funds held for clients		106.7	91.8	206.1	181.0
PEO revenues (A)	[1]	939.9	818.1	1,838.3	1,608.4
TOTAL REVENUES		3,235.4	2,987.3	6,314.2	5,904.2
Costs of revenues:
Operating expenses		1,719.3	1,560.4	3,366.0	3,091.9
Systems development and programming costs		158.1	152.5	315.1	307.4
Depreciation and amortization		69.3	54.9	131.9	112.2
TOTAL COSTS OF REVENUES		1,946.7	1,767.8	3,813.0	3,511.5
Selling, general, and administrative expenses		717.2	640.8	1,379.6	1,288.6
Interest expense		27.5	20.5	55.5	40.4
TOTAL EXPENSES		2,691.4	2,429.1	5,248.1	4,840.5
Other income, net		(21.7)	(228.0)	(47.8)	(251.1)
EARNINGS BEFORE INCOME TAXES		565.7	786.2	1,113.9	1,314.8
Provision for income taxes		98.2	275.3	244.9	435.2
NET EARNINGS		$ 467.5	$ 510.9	$ 869.0	$ 879.6
Basic earnings per share (in US$ per share)		$ 1.06	$ 1.14	$ 1.97	$ 1.95
Diluted earnings per share (in US$ per share)		$ 1.05	$ 1.13	$ 1.96	$ 1.94
Basic weighted average shares outstanding (shares)		441.3	447.9	441.8	450.1
Diluted weighted average shares outstanding (shares)		443.7	450.3	444.4	452.7
Dividends declared per common share (in US$ per share)		$ 0.630	$ 0.570	$ 1.200	$ 1.100

[1] Professional Employer Organization (“PEO”) revenues are net of direct pass-through costs, primarily consisting of payroll wages and payroll taxes of $10,632.3 million and $9,145.5 million for the three months ended December 31, 2017 and 2016, respectively, and $19,370.8 million and $16,833.1 million for the six months ended December 31, 2017 and 2016, respectively.