Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		May 31, 2019	May 31, 2018	May 31, 2017
Allowance For Doubtful Accounts [Member]
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Beginning Balance		$ 199	$ 115	$ 73
Charged To Expenses		295	246	136
Deductions	[1]	373	162	94
Valuation Allowances And Reserves Ending Balance		121	199	115
Allowance For Revenue Adjustments [Member]
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Beginning Balance		202	137	105
Charged To Other Accounts	[2]	1,192	1,173	941
Deductions	[3]	1,215	1,108	909
Valuation Allowances And Reserves Ending Balance		179	202	137
Inventory Valuation Allowance [Member]
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Beginning Balance		268	237	218
Charged To Expenses		28	27	26
Charged To Other Accounts		75	6
Deductions		36	2	7
Valuation Allowances And Reserves Ending Balance		$ 335	$ 268	$ 237

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

[2] Principally charged against revenue.

[3] Service failures, rebills and other.