CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - 6 months ended Sep. 30, 2016 - 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]
Balance (in shares) at Mar. 31, 2016		3,974		1
Balance at Mar. 31, 2016	$ 19,783	$ 40	$ 27,563	$ (3)	$ (7,378)	$ (439)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(444)				(444)
Other Comprehensive Income (Loss), Net of Tax	7					7
Stock Issued During Period, Shares, New Issues		7
Stock Issued During Period, Value, New Issues	20		17
Stock Issued During Period, Shares, Treasury Stock Reissued				(1)
Stock Issued During Period, Value, Treasury Stock Reissued				$ 3
Share-based compensation expense	29		29
Capital Contribution By SoftBank	28		28
Balance (in shares) at Sep. 30, 2016		3,981		0
Balance at Sep. 30, 2016	$ 19,423	$ 40	$ 27,637	$ 0	$ (7,822)	$ (432)