Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		May 31, 2021	May 31, 2020	May 31, 2019
Allowance For Doubtful Accounts [Member]
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Beginning Balance		$ 175	$ 121	$ 199
Charged To Expenses		577	442	295
Deductions	[1]	394	388	373
Valuation Allowances And Reserves Ending Balance		358	175	121
Allowance For Revenue Adjustments [Member]
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Beginning Balance		215	179	202
Charged To Other Accounts	[2]	1,892	1,286	1,192
Deductions	[3]	1,723	1,250	1,215
Valuation Allowances And Reserves Ending Balance		384	215	179
Inventory Valuation Allowance [Member]
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Beginning Balance		335	335	268
Charged To Expenses		38	33	28
Charged To Other Accounts				75
Deductions		24	33	36
Valuation Allowances And Reserves Ending Balance		$ 349	$ 335	$ 335

[1] Uncollectible accounts written off, net of recoveries, and other adjustments.

[2] Principally charged against revenue.

[3] Service failures, rebills and other.