Summary of Significant Accounting Policies - Revisions (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Aug. 31, 2014	Nov. 30, 2014	May. 31, 2015	May. 31, 2014	May. 31, 2013
Cash provided by operations:
Net income	$ 962	$ 1,617	$ 3,273	$ 2,693	$ 2,472
Amortization and other	8	15	43	68	64
Net foreign currency adjustments	53	243	424	56	66
Cash provided by operations	683	1,547	4,680	3,013	3,032
Cash used by investing activities:
Effect of exchange rate changes on cash and equivalents	2	(24)	(83)	(9)	36
Cash used by financing activities:
Net increase (decrease) in cash and equivalents	83	53	1,632	(1,117)	1,083
Cash and equivalents, beginning of year	2,220	2,220	2,220	3,337	2,254
CASH AND EQUIVALENTS, END OF YEAR	2,303	2,273	3,852	2,220	3,337
As Reported
Cash provided by operations:
Net income	962	1,617		2,693	2,472
Amortization and other	(34)	(54)		114	66
Net foreign currency adjustments	0	0		0	0
Cash provided by operations	588	1,235		3,003	2,968
Cash used by investing activities:
Effect of exchange rate changes on cash and equivalents	97	288		1	100
Cash used by financing activities:
Net increase (decrease) in cash and equivalents	83	53		(1,117)	1,083
Cash and equivalents, beginning of year	2,220	2,220	2,220	3,337	2,254
CASH AND EQUIVALENTS, END OF YEAR	2,303	2,273		2,220	3,337
Prior Period Revisions to Foreign Currency Adjustments
Cash used by financing activities:
Net increase (decrease) in cash and equivalents			0	0
Prior Period Revisions to Foreign Currency Adjustments | Scenario, Adjustment
Cash provided by operations:
Net income	0	0		0	0
Amortization and other	42	69		(46)	(2)
Net foreign currency adjustments	53	243		56	66
Cash provided by operations	95	312		10	64
Cash used by investing activities:
Effect of exchange rate changes on cash and equivalents	(95)	(312)		(10)	(64)
Cash used by financing activities:
Net increase (decrease) in cash and equivalents	0	0		0	0
Cash and equivalents, beginning of year	0	0	0	0	0
CASH AND EQUIVALENTS, END OF YEAR	$ 0	$ 0	$ 0	$ 0	$ 0