Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Jan. 31, 2013 Country	Jul. 31, 2012	Jan. 31, 2012	Jul. 31, 2011	Jan. 31, 2013 Segment Country	Jan. 31, 2012	Apr. 30, 2012
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of offices	76				76
Number of countries in which entity operates	35				35
Number of business segments					3
Investments in affiliated companies maximum	50.00%				50.00%
Restricted cash	$ 2.9				$ 2.9		$ 10.0
Performance related bonus expenses	28.0		23.1		82.0	84.0
Decrease in performance related bonus expenses		(0.2)		(1.2)
Performance related bonus after reduction in the previous year estimate					$ 81.8	$ 82.8
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Intangible assets estimated useful lives					3 years
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Intangible assets estimated useful lives					24 years