Accounting Policies (Details) - USD ($) $ in Millions	9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Accounting Policies [Abstract]
Percentage of cash and cash equivalents held by the Company's foreign subsidiaries outside the United States	66.00%
Accounting Policies [Line Items]
Payments related to tax withholding for share-based compensation	$ 35	$ 34
ASU 2014-09 (ASC Topic 606)
Accounting Policies [Line Items]
Period of estimated additional income tax payments upon adoption of ASC Topic 606	4 years
ASU 2014-09 (ASC Topic 606) | Tax Cuts and Jobs Act [Member]
Accounting Policies [Line Items]
Period of estimated additional income tax payments upon adoption of ASC Topic 606, Net of benefits from Tax Cuts and Jobs Act	4 years
ASU 2014-09 (ASC Topic 606) | Minimum
Accounting Policies [Line Items]
Estimated additional income tax payments per year upon adoption of ASC Topic 606, Gross	$ 100
Capitalized contract costs, Amortization period	4 years
ASU 2014-09 (ASC Topic 606) | Minimum | Tax Cuts and Jobs Act [Member]
Accounting Policies [Line Items]
Estimated additional income tax payments per year upon adoption of ASC Topic 606, Net of benefits from Tax Cuts and Jobs Act	$ 25
ASU 2014-09 (ASC Topic 606) | Maximum
Accounting Policies [Line Items]
Estimated additional income tax payments per year upon adoption of ASC Topic 606, Gross	$ 150
Capitalized contract costs, Amortization period	7 years
ASU 2014-09 (ASC Topic 606) | Maximum | Tax Cuts and Jobs Act [Member]
Accounting Policies [Line Items]
Estimated additional income tax payments per year upon adoption of ASC Topic 606, Net of benefits from Tax Cuts and Jobs Act	$ 50
Reclass from Operating Activities to Financing Activities | ASU 2016-09
Accounting Policies [Line Items]
Payments related to tax withholding for share-based compensation		$ 34
Other Noncurrent Assets, Net
Accounting Policies [Line Items]
Restricted cash	$ 3		$ 1