Goodwill and Intangible Assets (Details) (USD $)	12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 EMB [Member]	Jun. 30, 2012 Benefits [Member]	Jun. 30, 2011 Benefits [Member]	Jun. 30, 2012 Risk And Financial Services [Member]	Jun. 30, 2011 Risk And Financial Services [Member]	Jun. 30, 2012 Talent And Rewards [Member]	Jun. 30, 2011 Talent And Rewards [Member]	Jun. 30, 2012 Exchange Solutions [Member]	Jun. 30, 2012 All Other [Member]	Jun. 30, 2011 All Other [Member]	Jun. 30, 2010 All Other [Member]
Goodwill [Roll Forward]
Goodwill as at	$ 1,943,574,000	$ 1,717,295,000		$ 1,288,359,000	$ 1,151,681,000	$ 538,764,000	$ 459,373,000	$ 115,237,000	$ 105,027,000	$ 0	$ 1,214,000	$ 1,214,000	$ 1,214,000
Goodwill acquired	377,643,000	101,110,000		13,867,000	49,769,000	22,764,000	49,150,000		2,191,000	341,012,000
Translation adjustment	(68,662,000)	125,169,000		(48,971,000)	86,909,000	(15,666,000)	30,241,000	(4,025,000)	8,019,000
Goodwill as at	2,252,555,000	1,943,574,000		1,253,255,000	1,288,359,000	545,862,000	538,764,000	111,212,000	115,237,000	341,012,000	1,214,000	1,214,000	1,214,000
Goodwill adjustment for deferred taxes			$ (8,200,000)