Consolidated Condensed Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-In Capital	Retained Earnings	Other Accumulated Comprehensive Loss	Treasury Stock
Balance (shares) at May. 31, 2018		182,723				76,397
Balance at May. 31, 2018	$ 3,016,526	$ 618,464	$ 245,211	$ 5,837,827	$ 16,343	$ (3,701,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	212,515			212,515
Comprehensive income (loss), net of tax	(6,482)				(6,482)
Dividends	1			1
Stock-based compensation	46,172		46,172
Vesting of stock-based compensation awards (shares)		739
Vesting of stock-based compensation awards		$ 151,012	(151,012)
Stock options exercised, net of shares surrendered (in shares)		594
Stock options exercised, net of shares surrendered	27,512	$ 27,512
Repurchase of common stock (shares)						(689)
Repurchase of common stock	(139,468)					$ (139,468)
Balance (shares) at Aug. 31, 2018		184,056				77,086
Balance at Aug. 31, 2018	3,345,968	$ 796,988	140,371	6,239,535	9,861	$ (3,840,787)
Balance (shares) at May. 31, 2018		182,723				76,397
Balance at May. 31, 2018	3,016,526	$ 618,464	245,211	5,837,827	16,343	$ (3,701,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	455,528
Comprehensive income (loss), net of tax	(12,478)
Balance (shares) at Nov. 30, 2018		184,153				79,029
Balance at Nov. 30, 2018	3,027,244	$ 804,234	166,837	6,261,756	3,865	$ (4,209,448)
Balance (shares) at Aug. 31, 2018		184,056				77,086
Balance at Aug. 31, 2018	3,345,968	$ 796,988	140,371	6,239,535	9,861	$ (3,840,787)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	243,013			243,013
Comprehensive income (loss), net of tax	(5,996)				(5,996)
Dividends	(220,792)			(220,792)
Stock-based compensation	28,612		28,612
Vesting of stock-based compensation awards (shares)		11
Vesting of stock-based compensation awards		$ 2,146	(2,146)
Stock options exercised, net of shares surrendered (in shares)		86
Stock options exercised, net of shares surrendered	5,100	$ 5,100
Repurchase of common stock (shares)						(1,943)
Repurchase of common stock	(368,661)					$ (368,661)
Balance (shares) at Nov. 30, 2018		184,153				79,029
Balance at Nov. 30, 2018	3,027,244	$ 804,234	166,837	6,261,756	3,865	$ (4,209,448)
Balance (shares) at May. 31, 2019		184,791				81,506
Balance at May. 31, 2019	3,002,721	$ 840,328	227,928	6,691,236	(39,152)	$ (4,717,619)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	250,812			250,812
Comprehensive income (loss), net of tax	(23,474)				(23,474)
Stock-based compensation	40,395		40,395
Vesting of stock-based compensation awards (shares)		605
Vesting of stock-based compensation awards		$ 157,882	(157,882)
Stock options exercised, net of shares surrendered (in shares)		557
Stock options exercised, net of shares surrendered	37,915	$ 37,915
Repurchase of common stock (shares)						(1,082)
Repurchase of common stock	(256,830)					$ (256,830)
Balance (shares) at Aug. 31, 2019		185,953				82,588
Balance at Aug. 31, 2019	3,050,706	$ 1,036,125	110,441	6,939,240	(60,651)	$ (4,974,449)
Balance (shares) at May. 31, 2019		184,791				81,506
Balance at May. 31, 2019	3,002,721	$ 840,328	227,928	6,691,236	(39,152)	$ (4,717,619)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	496,932
Comprehensive income (loss), net of tax	342
Balance (shares) at Nov. 30, 2019		186,298				82,595
Balance at Nov. 30, 2019	3,104,970	$ 1,066,814	134,041	6,917,310	(36,835)	$ (4,976,360)
Balance (shares) at Aug. 31, 2019		185,953				82,588
Balance at Aug. 31, 2019	3,050,706	$ 1,036,125	110,441	6,939,240	(60,651)	$ (4,974,449)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	246,120			246,120
Comprehensive income (loss), net of tax	23,816				23,816
Dividends	(268,050)			(268,050)
Stock-based compensation	29,003		29,003
Vesting of stock-based compensation awards (shares)		21
Vesting of stock-based compensation awards		$ 5,403	(5,403)
Stock options exercised, net of shares surrendered (in shares)		324
Stock options exercised, net of shares surrendered	25,286	$ 25,286
Repurchase of common stock (shares)						(7)
Repurchase of common stock	(1,911)					$ (1,911)
Balance (shares) at Nov. 30, 2019		186,298				82,595
Balance at Nov. 30, 2019	$ 3,104,970	$ 1,066,814	$ 134,041	$ 6,917,310	$ (36,835)	$ (4,976,360)