Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Capital in Excess of Stated Value	Accumulated Other Comprehensive Income	Retained Earnings	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
Beginning Balance (in shares) at May. 31, 2015						355		1,357
Beginning balance at May. 31, 2015	$ 12,707	$ 4,165	$ 1,246	$ 7,293		$ 0		$ 3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised (in shares)								22
Stock options exercised	680	680
Conversion to Class B Common Stock (in shares)						(2)		2
Conversion to Class B Common Stock	0
Repurchase of Class B Common Stock (in shares)								(55)
Repurchase of Class B Common Stock	(3,238)	(148)		(3,090)
Dividends on common stock and preferred stock	(1,053)			(1,053)
Issuance of shares to employees, net of shares withheld for employee taxes (in shares)								3
Issuance of shares to employees, net of shares withheld for employee taxes	94	105		(11)
Stock-based compensation	236	236
Net income	3,760			3,760
Other comprehensive income (loss)	(928)		(928)
Ending Balance (in shares) at May. 31, 2016						353		1,329
Ending balance at May. 31, 2016	12,258	5,038	318	6,899		$ 0		$ 3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised (in shares)								17
Stock options exercised	525	525
Conversion to Class B Common Stock (in shares)						(24)		24
Conversion to Class B Common Stock	0
Repurchase of Class B Common Stock (in shares)								(60)
Repurchase of Class B Common Stock	(3,249)	(189)		(3,060)
Dividends on common stock and preferred stock	(1,159)			(1,159)
Issuance of shares to employees, net of shares withheld for employee taxes (in shares)								4
Issuance of shares to employees, net of shares withheld for employee taxes	108	121		(13)
Stock-based compensation	215	215
Net income	4,240			4,240
Other comprehensive income (loss)	(531)		(531)
Ending Balance (in shares) at May. 31, 2017					329	329	1,314	1,314
Ending balance at May. 31, 2017	12,407	5,710	(213)	6,907		$ 0		$ 3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised (in shares)								24
Stock options exercised	600	600
Conversion to Class B Common Stock (in shares)						0		0
Conversion to Class B Common Stock	0
Repurchase of Class B Common Stock (in shares)								(70)
Repurchase of Class B Common Stock	(4,267)	(254)		(4,013)
Dividends on common stock and preferred stock	(1,265)			(1,265)
Issuance of shares to employees, net of shares withheld for employee taxes (in shares)								4
Issuance of shares to employees, net of shares withheld for employee taxes	82	110		(28)
Stock-based compensation	218	218
Net income	1,933			1,933
Other comprehensive income (loss)	104		104
Ending Balance (in shares) at May. 31, 2018					329	329	1,273	1,272
Ending balance at May. 31, 2018	$ 9,812	$ 6,384	(92)	3,517		$ 0		$ 3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassifications to retained earnings in accordance with ASU 2018-02 | Accounting Standards Update 2018-02			$ 17	$ (17)