Description Of Business And Basis of Presentation (Impact of Recently Adopted Accounting Standards) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Apr. 01, 2019	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 193	$ 215
Operating Lease, Liability, Current	69	50	$ 0
Operating Lease, Liability, Noncurrent	155	197
Prepaid Rent			6
Deferred Rent Credit			38
Consolidated Balance Sheet Statements, Captions [Line Items]
Other current assets	321	307	313
Other assets	305	329	114
Accrued and other current liabilities	1,052	1,099	1,052
Other liabilities	$ 216	294	$ 132
Balance Sheet Impact at Period End [Member]
Consolidated Balance Sheet Statements, Captions [Line Items]
Other current assets		(6)
Other assets		215
Accrued and other current liabilities		47
Other liabilities		$ 162