Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Millions		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2020
Property, Plant, and Equipment - Useful Life [Abstract]
Change in depreciation		$ (225)
Building
Property, Plant, and Equipment - Useful Life [Abstract]
Property, plant and equipment useful life		40 years
Computers and related equipment | Minimum
Property, Plant, and Equipment - Useful Life [Abstract]
Property, plant and equipment useful life	4 years	4 years
Computers and related equipment | Maximum
Property, Plant, and Equipment - Useful Life [Abstract]
Property, plant and equipment useful life	5 years	7 years
Furniture and other equipment | Minimum
Property, Plant, and Equipment - Useful Life [Abstract]
Property, plant and equipment useful life		3 years
Furniture and other equipment | Maximum
Property, Plant, and Equipment - Useful Life [Abstract]
Property, plant and equipment useful life		15 years
Leasehold improvements | Maximum
Property, Plant, and Equipment - Useful Life [Abstract]
Property, plant and equipment useful life		20 years