Acquisitions, Goodwill, and Acquired Intangible Assets - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
	Apr. 12, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired		$ 13	$ 45	$ 13,939	$ 146
Acquisition of Certain Other Companies
Business Acquisition [Line Items]
Aggregate purchase price		$ 39
Subsequent Event [Member] | Ring, Inc [Member]
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired	$ 900