Investments (Contractual Maturities Of AFS Debt Securities At Varying Dates Over The Next 30 Years) (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2014	Apr. 30, 2013	Jan. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Contractual maturities of AFS debt securities, Cost Basis, Total	$ 453,231	$ 480,628	$ 391,933
Contractual maturities of AFS debt securities, Fair Value, Total	443,770	486,876	397,313
Two to Five Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Contractual maturities of AFS debt securities, Cost Basis, Total	4,134
Contractual maturities of AFS debt securities, Fair Value, Total	4,375
Beyond [Member]
Schedule of Available-for-sale Securities [Line Items]
Contractual maturities of AFS debt securities, Cost Basis, Total	449,097
Contractual maturities of AFS debt securities, Fair Value, Total	$ 439,395