CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interest [Member]
Total stockholders' equity				$ 0
Net Income (Loss) Attributable to Parent	$ 176				$ 176
Balance (in shares) at Mar. 31, 2018		4,005
Beginning Balance at Mar. 31, 2018	26,419	$ 40	$ 27,884		(1,255)	$ (313)	$ 63
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	173						(3)
Other Comprehensive Income, Other, Net of Tax						4
Stock Issued During Period, Shares, New Issues		8
Stock Issued During Period, Value, New Issues	(2)		2
Stock Issued During Period, Shares, Treasury Stock Reissued				1
Stock Issued During Period, Value, Treasury Stock Reissued				$ (4)
Share-based compensation expense	40		40
Capital contribution by SoftBank	1		1
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	1,315
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	(8)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	1,307
Other, net	3		(3)
Cumulative effect of accounting change	0		8				(8)
Balance (in shares) at Jun. 30, 2018		4,013		1
Ending Balance at Jun. 30, 2018	27,945	$ 40	27,938		236	(317)	52
Total stockholders' equity				$ (4)
Total stockholders' equity	26,072			$ 0
Net Income (Loss) Attributable to Parent	(111)				(111)
Balance (in shares) at Mar. 31, 2019		4,081
Beginning Balance at Mar. 31, 2019	26,127	$ 41	28,306		(1,883)	(392)	55
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(114)						(3)
Other Comprehensive Income, Other, Net of Tax						(22)
Stock Issued During Period, Shares, New Issues		11
Stock Issued During Period, Value, New Issues	(17)		(15)
Stock Issued During Period, Shares, Treasury Stock Reissued				0
Stock Issued During Period, Value, Treasury Stock Reissued				$ (2)
Share-based compensation expense	35		35
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	162
Other, net	(3)		3
Cumulative effect of accounting change	162		0				0
Balance (in shares) at Jun. 30, 2019		4,092		0
Ending Balance at Jun. 30, 2019	26,168	$ 41	$ 28,323		$ (1,832)	$ (414)	$ 52
Total stockholders' equity	$ 26,116			$ (2)