XML 17 R37.htm IDEA: XBRL DOCUMENT v2.4.0.6
Components of Net Periodic Benefit Costs (Detail) (Deferred Compensation Plan, USD $)
In Thousands, unless otherwise specified
3 Months Ended
Jul. 31, 2012
Jul. 31, 2011
Deferred Compensation Plan
   
Defined Benefit Plan Disclosure [Line Items]    
Interest cost $ 756 $ 884
Amortization of actuarial loss 594 355
Net periodic benefit costs $ 1,350 $ 1,239