Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-In Capital	Retained Earnings	Other Accumulated Comprehensive Income (Loss)	Treasury Stock
Balance (shares) at May. 31, 2013		174,786				52,505
Beginning Balance at May. 31, 2013	$ 2,201,492	$ 186,332	$ 109,822	$ 3,717,771	$ 38,123	$ (1,850,556)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	374,442			374,442
Comprehensive income (loss), net of tax	(9,695)				(9,695)
Dividends	(93,320)			(93,320)
Stock-based compensation	44,746		44,746
Vesting of stock-based compensation awards (shares)		465
Vesting of stock-based compensation awards	0	$ 23,519	(23,519)
Stock options exercised, net of shares surrendered (shares)		1,127
Stock options exercised, net of shares surrendered		$ 41,902
Stock options exercised, net of shares surrendered	41,902
Repurchase of common stock (shares)						(6,836)
Repurchase of common stock	(370,599)					$ (370,599)
Other	3,890		3,890
Balance (shares) at May. 31, 2014		176,378				59,341
Ending Balance at May. 31, 2014	2,192,858	$ 251,753	134,939	3,998,893	28,428	$ (2,221,155)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	430,618			430,618
Comprehensive income (loss), net of tax	(36,899)				(36,899)
Dividends	(201,891)			(201,891)
Stock-based compensation	47,002		47,002
Vesting of stock-based compensation awards (shares)		575
Vesting of stock-based compensation awards	0	$ 37,265	(37,265)
Stock options exercised, net of shares surrendered (shares)		1,164
Stock options exercised, net of shares surrendered		$ 40,230
Stock options exercised, net of shares surrendered	40,230
Repurchase of common stock (shares)						(7,073)
Repurchase of common stock	(551,970)					$ (551,970)
Other	12,507		12,507
Balance (shares) at May. 31, 2015		178,117				66,414
Ending Balance at May. 31, 2015	1,932,455	$ 329,248	157,183	4,227,620	(8,471)	$ (2,773,125)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	693,520			693,520
Comprehensive income (loss), net of tax	(16,403)				(16,403)
Dividends	(115,273)			(115,273)
Stock-based compensation	79,293		79,293
Vesting of stock-based compensation awards (shares)		605
Vesting of stock-based compensation awards	0	$ 52,208	(52,208)
Stock options exercised, net of shares surrendered (shares)		876
Stock options exercised, net of shares surrendered		$ 28,226
Stock options exercised, net of shares surrendered	28,226
Repurchase of common stock (shares)						(8,971)
Repurchase of common stock	(780,151)					$ (780,151)
Other	20,992		20,992
Balance (shares) at May. 31, 2016		179,598				75,385
Ending Balance at May. 31, 2016	$ 1,842,659	$ 409,682	$ 205,260	$ 4,805,867	$ (24,874)	$ (3,553,276)