Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2012	Apr. 30, 2013
Investments, Debt and Equity Securities [Abstract]
Other-than-temporary impairments of AFS securities	$ 12.4	$ 12.4
Held-to-maturity Securities			$ 1.9