Annual report pursuant to Section 13 and 15(d)

Changes in Each Component of Accumulated Other Comprehensive (Loss) Income (Detail)

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Changes in Each Component of Accumulated Other Comprehensive (Loss) Income (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Apr. 30, 2017
Apr. 30, 2016
Apr. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Beginning balance $ 1,045,300    
Unrealized (losses) gains arising during the period (15,071) $ (19,077) $ (40,122)
Reclassification of realized net losses to net income 1,918 1,789 1,887
Ending balance 1,083,439 1,045,300  
Accumulated Translation Adjustment      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Beginning balance (36,339) (20,919) 15,604
Unrealized (losses) gains arising during the period (19,020) (15,420) (36,523)
Ending balance (55,359) (36,339) (20,919)
Accumulated Defined Benefit Plan Adjustment      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Beginning balance [1] (21,572) (19,708) (18,006)
Unrealized (losses) gains arising during the period [1] 4,584 (3,653) (3,589)
Reclassification of realized net losses to net income [1] 1,861 1,789 1,887
Ending balance [1] (15,127) (21,572) (19,708)
Accumulated Net Unrealized Investment Gain (Loss)      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Beginning balance   4 14
Unrealized (losses) gains arising during the period   (4) (10)
Ending balance     4
Unrealized Losses on Interest Rate Swap      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Unrealized (losses) gains arising during the period [2] (635)    
Reclassification of realized net losses to net income [2] 57    
Ending balance [2] (578)    
Accumulated Other Comprehensive Income (Loss)      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Beginning balance (57,911) (40,623) (2,388)
Unrealized (losses) gains arising during the period (15,071) (19,077) (40,122)
Reclassification of realized net losses to net income 1,918 1,789 1,887
Ending balance $ (71,064) $ (57,911) $ (40,623)
[1] The tax effects on unrealized gains (losses) were $1.9 million, $(2.3) million and $(2.3) million as of April 30, 2017, 2016 and 2015, respectively. The tax effects on reclassifications of realized net losses were $1.2 million, $1.1 million and $1.2 million as of April 30, 2017, 2016 and 2015, respectively.
[2] The tax effects on unrealized (losses) were $(0.4) million as of April 30, 2017.