Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 933,624	$ 1,181,347
Other comprehensive income (loss) before reclassifications	38,994	(28,081)
Amounts reclassified from Accumulated Other Comprehensive Loss	2,385	795
Total Other Comprehensive Income (Loss)	41,379	(27,286)
Balance	973,745	1,132,006
Accumulated Other Comprehensive Loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(575,497)	(508,738)
Balance	(534,118)	(536,024)
Foreign Currency Translation [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(340,703)	(312,107)
Other comprehensive income (loss) before reclassifications	46,853	(35,539)
Amounts reclassified from Accumulated Other Comprehensive Loss	0	0
Total Other Comprehensive Income (Loss)	46,853	(35,539)
Balance	(293,850)	(347,646)
Unamortized Retirement Costs [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(227,920)	(196,057)
Other comprehensive income (loss) before reclassifications	(7,190)	7,130
Amounts reclassified from Accumulated Other Comprehensive Loss	1,525	1,038
Total Other Comprehensive Income (Loss)	(5,665)	8,168
Balance	(233,585)	(187,889)
Interest Rate Swaps [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(6,874)	(574)
Other comprehensive income (loss) before reclassifications	(669)	328
Amounts reclassified from Accumulated Other Comprehensive Loss	860	(243)
Total Other Comprehensive Income (Loss)	191	85
Balance	$ (6,683)	$ (489)