Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment—at cost	$ 7,137	$ 7,049
Less: accumulated depreciation	3,958	3,686
Property and equipment, net	3,179	3,363
Depreciation expense	820	709	$ 338
Land, buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment—at cost	2,180	2,464
Computers and related equipment
Property, Plant and Equipment [Line Items]
Property and equipment—at cost	4,719	4,185
Furniture and other equipment
Property, Plant and Equipment [Line Items]
Property and equipment—at cost	224	323
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment—at cost	$ 14	$ 77