CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock [Member]	Paid-in Capital [Member]	Treasury Shares [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Noncontrolling Interest [Member]
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ (1,995)
Balance (in shares) at Mar. 31, 2015		3,967,000,000		1,000,000
Balance at Mar. 31, 2015	21,710	$ 40	$ 27,468	$ (7)	$ (5,383)	$ (408)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(1,995)				(1,995)
Other comprehensive (loss) income	(31)					(31)
Issuance of common stock, net (in shares)		7,000,000
Issuance of common stock, net	10		6
Issuance (repurchase) of common stock, net				$ 4
Share-based compensation expense	71		71
Capital contribution by SoftBank			14
Other, net			4
Balance (in shares) at Mar. 31, 2016		3,974,000,000		1,000,000
Balance at Mar. 31, 2016	19,783	$ 40	27,563	$ (3)	(7,378)	(439)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(1,206)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(1,206)				(1,206)
Other comprehensive (loss) income	35					35
Issuance of common stock, net (in shares)		15,000,000
Issuance of common stock, net	50		47
Issuance (repurchase) of common stock, net (in shares)				(1,000,000)
Issuance (repurchase) of common stock, net				$ 3
Share-based compensation expense	91		91
Capital contribution by SoftBank			6
Other, net			49
Balance (in shares) at Mar. 31, 2017		3,989,000,000		0
Balance at Mar. 31, 2017	18,808	$ 40	27,756	$ 0	(8,584)	(404)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 18,808
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares, issued	3,989,000,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest							$ (12)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 7,377
Net (loss) income	7,389				7,389
Other comprehensive (loss) income	31					31
Issuance of common stock, net (in shares)		16,000,000
Issuance of common stock, net	21		21
Share-based compensation expense	182		182
Capital contribution by SoftBank			6
Other, net			(54)
Balance (in shares) at Mar. 31, 2018		4,005,000,000		0
Balance at Mar. 31, 2018	26,356	$ 40	27,884	$ 0	(1,255)	(313)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Tax Act reclassification	0				$ (60)	$ 60
Noncontrolling Interest, Period Increase (Decrease)	48		$ (27)				75
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 26,419						$ 63
Common stock, shares, issued	4,005,000,000