Consolidated Statements Of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock
Beginning Balances, Shares at Apr. 30, 2013		(316,628)				(43,993)
Beginning Balances, Value at Apr. 30, 2013	$ 1,263,547	$ 3,166	$ 752,483	$ 10,550	$ 1,333,445	$ (836,097)
Net income	475,157				475,157
Other comprehensive income (loss)	(5,373)			(5,373)
Stock-based compensation	20,058		20,058
Stock-based awards exercised or vested, value	(28,246)		(5,887)		(325)	$ (34,458)
Stock-based awards exercised or vested, shares						1,811
Shares issued for:
Acquisition of treasury shares, shares						(218)
Acquisition of treasury shares, value	(6,106)					$ (6,106)
Cash dividends declared	(218,980)				(218,980)
Ending Balances, Shares at Apr. 30, 2014		(316,628)				(42,400)
Ending Balances, Value at Apr. 30, 2014	1,556,549	$ 3,166	766,654	5,177	1,589,297	$ (807,745)
Net income	473,663				473,663
Other comprehensive income (loss)	(3,437)			(3,437)
Stock-based compensation	26,068		26,068
Stock-based awards exercised or vested, value	(16,131)		(8,881)		(942)	$ (25,954)
Stock-based awards exercised or vested, shares						1,359
Acquisition of treasury shares	(10,449)		0			$ (10,449)
Shares issued for:
Option exercises, shares						(315)
Acquisition of treasury shares, shares						0
Acquisition of treasury shares, value	(219,960)					$ 0
Other, value	(5,616)		(48)		(5,616)	$ 48
Other, shares						3
Cash dividends declared					(219,960)
Ending Balances, Shares at Apr. 30, 2015		(316,628)				(41,353)
Ending Balances, Value at Apr. 30, 2015	1,832,949	$ 3,166	783,793	1,740	1,836,442	$ (792,192)
Net income	374,267				374,267
Other comprehensive income (loss)	(12,973)			(12,973)
Stock-based compensation	23,540		23,540
Stock-based awards exercised or vested, value	(25,346)		(15,257)		(2,848)	$ (43,451)
Stock-based awards exercised or vested, shares						2,262
Acquisition of treasury shares	(18,102)		0			$ (18,102)
Stock Repurchased During Period, Shares		(56,409)
Stock Repurchased During Period, Value	$ (2,000,236)	$ (564)	(33,846)		(1,965,826)
Shares issued for:
Option exercises, shares	(707)					(610)
Acquisition of treasury shares, shares						0
Acquisition of treasury shares, value	$ (201,688)					$ 0
Cash dividends declared					(201,688)
Ending Balances, Shares at Apr. 30, 2016		(260,219)				(39,701)
Ending Balances, Value at Apr. 30, 2016	$ 23,103	$ 2,602	$ 758,230	$ (11,233)	$ 40,347	$ (766,843)