Consolidated Statements of Changes in Common Stockholders' Investment - USD ($) $ in Millions		12 Months Ended
		May 31, 2021	May 31, 2020	May 31, 2019
Beginning Balance		$ 18,295	$ 17,757	$ 19,416
Net income		5,231	1,286	540
Other comprehensive gain (loss), net of tax		415	(333)	(287)
Purchase of treasury stock			(3)	(1,480)
Cash dividends declared		(686)	(679)	(683)
Employee incentive plans and other		913	220	251
Ending Balance		24,168	18,295	17,757
Accounting Standards Update 2018-02
Reclassification to retained earnings due to the adoption of a new accounting standard on June 1, 2019	[1]		51
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-02 and 2018-02
Beginning Balance	[2]	(4)
Ending Balance	[2]		(4)
Common Stock
Beginning Balance		32	32	32
Ending Balance		32	32	32
Additional Paid-In Capital
Beginning Balance		3,356	3,231	3,117
Employee incentive plans and other		125	125	114
Ending Balance		3,481	3,356	3,231
Retained Earnings
Beginning Balance		25,216	24,648	24,823
Net income		5,231	1,286	540
Cash dividends declared		(686)	(679)	(683)
Employee incentive plans and other		56	(35)	(32)
Ending Balance		29,817	25,216	24,648
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-02 and 2018-02
Beginning Balance	[2]	(4)
Ending Balance	[2]		(4)
Accumulated Other Comprehensive Loss
Beginning Balance		(1,147)	(865)	(578)
Other comprehensive gain (loss), net of tax		415	(333)	(287)
Ending Balance		(732)	(1,147)	(865)
Accumulated Other Comprehensive Loss | Accounting Standards Update 2018-02
Reclassification to retained earnings due to the adoption of a new accounting standard on June 1, 2019	[1]		51
Treasury Stock
Beginning Balance		(9,162)	(9,289)	(7,978)
Purchase of treasury stock			(3)	(1,480)
Employee incentive plans and other		732	130	169
Ending Balance		$ (8,430)	$ (9,162)	$ (9,289)

[1] ^{Relates to the adoption of ASU 2018-02.}

[2] ^{Relates to the adoption of Accounting Standards Update (“ASU”) 2016-02 and ASU 2018-02}