Summary of Significant Accounting Policies - Recently Adopted Accounting Standards (Details) - USD ($) $ in Millions	Feb. 29, 2020	Jun. 01, 2019	May 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Assets	$ 26,220		$ 23,717
Operating lease liability	3,180
Operating lease right-of-use assets	$ 2,907		$ 0
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Assets		$ 2,700
Liabilities		2,700
Operating lease liability		3,200
Operating lease right-of-use assets		2,900
Decrease in deferred rent liabilities		348
Build-to-suit lease asset removed		184
Build-to-suit lease liability removed		$ 184