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
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
Net Income (Loss) Attributable to Parent	372
Balance (in shares) at Mar. 31, 2018		4,005
Beginning Balance at Mar. 31, 2018	26,419	$ 40	27,884		(1,255)	(313)	63
Balance (in shares) at Sep. 30, 2018		4,079		2
Ending Balance at Sep. 30, 2018	28,464	$ 41	28,251		432	(308)	63
Total stockholders' equity				$ (4)
Net Income (Loss) Attributable to Parent	196				196
Balance (in shares) at Jun. 30, 2018		4,013		1
Beginning Balance at Jun. 30, 2018	27,945	$ 40	27,938		236	(317)	52
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	207						11
Other Comprehensive Income, Other, Net of Tax						9
Stock Issued During Period, Shares, New Issues		66
Stock Issued During Period, Value, New Issues	278	$ 1	288
Stock Issued During Period, Shares, Treasury Stock Reissued				1
Stock Issued During Period, Value, Treasury Stock Reissued				$ (11)
Share-based compensation expense	27		27
Capital contribution by SoftBank	1		1
Other, net	(3)		3
Balance (in shares) at Sep. 30, 2018		4,079		2
Ending Balance at Sep. 30, 2018	28,464	$ 41	28,251		432	(308)	63
Total stockholders' equity				$ (15)
Total stockholders' equity	26,072			$ 0
Net Income (Loss) Attributable to Parent					(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
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
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
Net Income (Loss) Attributable to Parent	(385)
Balance (in shares) at Mar. 31, 2019		4,081
Beginning Balance at Mar. 31, 2019	26,127	$ 41	28,306		(1,883)	(392)	55
Balance (in shares) at Sep. 30, 2019		4,108		2
Ending Balance at Sep. 30, 2019	25,897	$ 41	28,349		(2,106)	(418)	47
Total stockholders' equity				$ (2)
Net Income (Loss) Attributable to Parent	(274)				(274)
Balance (in shares) at Jun. 30, 2019		4,092		0
Beginning Balance at Jun. 30, 2019	26,168	$ 41	28,323		(1,832)	(414)	52
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(279)						(5)
Other Comprehensive Income, Other, Net of Tax						(4)
Stock Issued During Period, Shares, New Issues		16
Stock Issued During Period, Value, New Issues	(16)		(2)
Stock Issued During Period, Shares, Treasury Stock Reissued				2
Stock Issued During Period, Value, Treasury Stock Reissued				$ (14)
Share-based compensation expense	28		28
Balance (in shares) at Sep. 30, 2019		4,108		2
Ending Balance at Sep. 30, 2019	25,897	$ 41	$ 28,349		$ (2,106)	$ (418)	$ 47
Total stockholders' equity	$ 25,850			$ (16)