Goodwill and Intangible Assets, Net of Accumulated Amortization (Details) (USD $) In Millions, unless otherwise specified	Nov. 30, 2013	May 31, 2013
Components of intangible assets, at cost
Client lists	$ 236.2	$ 231.0
Other intangible assets	2.6	2.4
Total intangible assets, gross	238.8	233.4
Less: Accumulated amortization	195.2	188.2
Intangible assets, net of accumulated amortization	43.6	45.2
Estimated future amortization expense relating to intangible assets
Fiscal year ending May 31, 2014	15.7
Fiscal year ending May 31, 2015	12.0
Fiscal year ending May 31, 2016	8.8
Fiscal year ending May 31, 2017	6.3
Fiscal year ending May 31, 2018	$ 4.2