Description Of Business And Basis Of Presentation Description of Business and Basis of Presentation (Impact of Recently Adopted Accounting Standards) (Details) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Apr. 01, 2018		Mar. 31, 2018	[1]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)		$ 4,944		$ 4,652		$ 4,062
Increase (Decrease) in Deferred Revenue		(383)
Cost of Revenue		215	$ 154
Net revenue		1,137	1,449
Receivables, Net		371		543		$ 385
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)		300		590	[1]
Increase (Decrease) in Deferred Revenue	[1]	740
Cost of Revenue		49
Net revenue		(279)
Receivables, Net		129		$ 158	[1]
Product [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Revenue		68	64
Net revenue		202	828
Product [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Revenue		(10)
Net revenue		(514)
Service [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Revenue		147	90
Net revenue		935	$ 621
Service [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Revenue		59
Net revenue		$ 235
Transferred at Point in Time [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue, Information Used to Allocate Transaction Price		0.75
Transferred over Time [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue, Information Used to Allocate Transaction Price		0.25
Net revenue		$ 186
Mobile platform fees [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Revenue	[1]	64
Mobile platform fees [Member] | Service [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Revenue	[1]	$ 49

[1] Derived from audited Consolidated Financial Statements.