Segment Information (Narrative) (Details) (USD $)	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Segment Reporting Information [Line Items]
Revenues from international operations	$ 249,000,000	$ 232,800,000	$ 205,800,000
Pretax income from international operations	44,600,000	47,100,000	46,200,000
Assets	4,537,779,000	4,649,567,000	5,289,453,000
Foreign
Segment Reporting Information [Line Items]
Assets	$ 472,600,000	$ 201,800,000	$ 206,300,000