Summary of Significant Accounting Policies - Recently Adopted Accounting Standards (Details) - USD ($) $ in Millions	Aug. 31, 2019	Jun. 01, 2019	May 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability	$ 3,102
Operating lease right-of-use assets	2,832		$ 0
Assets	$ 26,249		$ 23,717
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability		$ 3,200
Operating lease right-of-use assets		2,900
Assets		2,700
Liabilities		2,700
Decrease in deferred rent liabilities		348
Build-to-suit lease asset		184
Build-to-suit lease liability		$ 184