Fair Value Measurements (Details) (Recurring basis, USD $) In Thousands, unless otherwise specified	Apr. 30, 2013
Assets:
Available-for-sale securities	$ 287
SERP assets – employer	926
SERP assets – employee	18,615
Hedge derivatives	212
Total	20,040
Liabilities:
SERP liabilities – employee	18,615
Hedge derivatives	111
Total	18,726
Level 1
Assets:
Available-for-sale securities	287
SERP assets – employer	926
SERP assets – employee	18,615
Hedge derivatives
Total	19,828
Liabilities:
SERP liabilities – employee	18,615
Hedge derivatives
Total	18,615
Level 2
Assets:
Hedge derivatives	212
Total	212
Liabilities:
Hedge derivatives	111
Total	111
Level 3
Assets:
Available-for-sale securities
SERP assets – employer
SERP assets – employee
Hedge derivatives
Total
Liabilities:
SERP liabilities – employee
Hedge derivatives
Total