Leases Schedule Of Supplemental Balance Sheet Information Related To Operating Leases (Details) - USD ($) $ in Millions	Dec. 31, 2019	Mar. 31, 2019
Lessor, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 1,182
Operating Lease, Liability, Current	252
Operating Lease, Liability, Noncurrent	978
Operating Lease, Liability	$ 1,230
Operating Lease, Weighted Average Remaining Lease Term	9 years
Operating Lease, Weighted Average Discount Rate, Percent	3.35%
Accounting Standards Update 2016-02 [Member]
Lessor, Lease, Description [Line Items]
Operating Lease, Liability	$ 1,230	$ 1,064