Description of Business and Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, $ in Millions	12 Months Ended
	May 31, 2017 USD ($) air-craft $ / shares shares	May 31, 2016 USD ($) $ / shares shares	May 31, 2015 USD ($) air-craft Engine $ / shares shares	Jan. 26, 2016 shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Advertising and promotion expenses	$ 458	$ 417	$ 403
Depreciable life range for majority of aircraft costs	15 to 30 years
Number of aircraft with shortened depreciable lives | air-craft			23
Number of aircraft engines with shortened depreciable lives | Engine			57
Depreciation expense, excluding gains and losses on sales of property and equipment	$ 2,900	2,600	$ 2,600
Interest Costs Capitalized	$ 41	$ 42	$ 37
Number of Idle Aircraft | air-craft	7
Number of months aircraft remained idle	an average of 12 months
Number of Impaired Boeing MD11 Aircraft | air-craft			7
Number of Impaired Boeing MD11 Aircraft Engines | Engine			12
Number of Impaired Airbus A310-300 Aircraft | air-craft			4
Number of Impaired Airbus A310-300 Aircraft Engines | Engine			3
Number of Impaired Airbus A300-600 Aircraft | air-craft			3
Number of Impaired Airbus A300-600 Aircraft Engines | Engine			3
Number of Impaired Boeing MD10-10 Aircraft | air-craft			1
Number of Impaired Boeing MD10-10 Aircraft Engines | Engine			3
Asset impairments			$ 276
Asset impairments, net of tax			$ 175
Asset impairments Diluted EPS impact | $ / shares			$ 0.61
Asset impairment non-cash			$ 246
Stock Repurchase Program, Number Of Shares Authorized To Be Repurchased | shares				25,000,000
Purchase of treasury stock | shares	3,000,000	18,200,000	8,100,000
Treasury Stock Acquired, Average Cost Per Share | $ / shares	$ 172.13	$ 149.35	$ 154.03
Payments for Repurchase of Common Stock	$ 509	$ 2,722	$ 1,254
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased | shares	16,000,000
Dividends Payable, Date Declared	Jun. 12, 2017
Dividends Payable Amount Per Share | $ / shares	$ 0.50
Dividends Payable, Date To Be Paid	Jul. 06, 2017
Dividends Payable, Date Of Record	Jun. 22, 2017
Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Intangible assets amortization periods	3 years
Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Intangible assets amortization periods	15 years