Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Other Accumulated Comprehensive Income (Loss)	Other Accumulated Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock
Balance (shares) at May. 31, 2017			180,993						75,592
Beginning Balance at May. 31, 2017	$ 2,302,793		$ 485,068	$ 223,924	$ 5,170,830		$ (3,029)		$ (3,574,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	842,586				842,586
Comprehensive income (loss), net of tax	19,372						19,372
Dividends	(175,589)				(175,589)
Stock-based compensation	112,835			112,835
Vesting of stock-based compensation awards (shares)			701
Vesting of stock-based compensation awards	0		$ 91,548	(91,548)
Stock options exercised, net of shares surrendered (in shares)			1,029
Stock options exercised, net of shares surrendered	41,848		$ 41,848
Repurchase of common stock (shares)									(805)
Repurchase of common stock	(127,319)								$ (127,319)
Balance (shares) at May. 31, 2018			182,723						76,397
Ending Balance at May. 31, 2018	3,016,526	$ 189,192	$ 618,464	245,211	5,837,827	$ 189,192	16,343		$ (3,701,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	884,981				884,981
Comprehensive income (loss), net of tax	(55,495)						(55,495)
Dividends	(220,764)				(220,764)
Stock-based compensation	139,210			139,210
Vesting of stock-based compensation awards (shares)			766
Vesting of stock-based compensation awards	0		$ 156,493	(156,493)
Stock options exercised, net of shares surrendered (in shares)			1,302
Stock options exercised, net of shares surrendered	65,371		$ 65,371
Repurchase of common stock (shares)									(5,109)
Repurchase of common stock	(1,016,300)								$ (1,016,300)
Balance (shares) at May. 31, 2019			184,791						81,506
Ending Balance at May. 31, 2019	3,002,721	$ (833)	$ 840,328	227,928	6,691,236	$ (2,808)	(39,152)	$ 1,975	$ (4,717,619)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	876,037				876,037
Comprehensive income (loss), net of tax	(116,203)						(116,203)
Dividends	(267,956)				(267,956)
Stock-based compensation	115,435			115,435
Vesting of stock-based compensation awards (shares)			641
Vesting of stock-based compensation awards	0		$ 171,842	(171,842)
Stock options exercised, net of shares surrendered (in shares)			1,361
Stock options exercised, net of shares surrendered	90,519		$ 90,519
Repurchase of common stock (shares)									(1,872)
Repurchase of common stock	(464,518)								$ (464,518)
Balance (shares) at May. 31, 2020			186,793						83,378
Ending Balance at May. 31, 2020	$ 3,235,202		$ 1,102,689	$ 171,521	$ 7,296,509		$ (153,380)		$ (5,182,137)