CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member] Class A [Member]	Common Stock [Member] Class B [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Class A [Member]	Retained Earnings [Member] Class B [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total	Class A [Member]	Class B [Member]
Balance at Apr. 30, 2013	$ 69,793	$ 13,397	$ 290,762	$ 1,387,512			$ (494,476)	$ (278,632)	$ 988,356
Restricted Shares Issued under Share-based Compensation Plans			(5,962)				6,144		182
Net (Payments)/Proceeds from Exercise of Stock Options and other			31,403				24,417		55,820
Shortfall in Tax Benefits from Share-based Compensation			(1,466)						(1,466)
Share-based compensation expense			12,851						12,851
Purchase of Treasury Shares							(63,393)		(63,393)
Common Stock Dividends					$ (51,842)	$ (7,111)				$ (51,842)	$ (7,111)
Common Stock Class Conversions	5	(5)							0
Comprehensive Income (Loss)				160,510				88,341	248,851
Balance at Apr. 30, 2014	69,798	13,392	327,588	1,489,069			(527,308)	(190,291)	1,182,248
Restricted Shares Issued under Share-based Compensation Plans			(3,471)				4,085		614
Net (Payments)/Proceeds from Exercise of Stock Options and other			12,093				13,230		25,323
Excess Tax Benefits from Share-based Compensation			3,191						3,191
Share-based compensation expense			13,617						13,617
Purchase of Treasury Shares							(61,981)		(61,981)
Common Stock Dividends					(57,541)	(10,957)				(57,541)	(10,957)
Comprehensive Income (Loss)				176,868				(216,342)	(39,474)
Balance at Apr. 30, 2015	69,798	13,392	353,018	1,597,439			(571,974)	(406,633)	1,055,040
Restricted Shares Issued under Share-based Compensation Plans			(3,152)				3,325		173
Net (Payments)/Proceeds from Exercise of Stock Options and other			1,700				(1,795)		(95)
Excess Tax Benefits from Share-based Compensation			1,027						1,027
Share-based compensation expense			16,105						16,105
Purchase of Treasury Shares							(69,977)		(69,977)
Common Stock Dividends					$ (58,658)	$ (11,238)				$ (58,658)	$ 11,238
Comprehensive Income (Loss)				145,782				(41,053)	104,729
Balance at Apr. 30, 2016	$ 69,798	$ 13,392	$ 368,698	$ 1,673,325			$ (640,421)	$ (447,686)	$ 1,037,106