CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Attributable to Parent	$ 7,389	$ (1,206)	$ (1,995)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	7,377	(1,206)	(1,995)
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustment	14	(1)	(11)
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	36	(2)	0
Net unrealized holding (losses) gains on securities	12	0	(1)
Unrecognized net periodic pension and other postretirement benefits:
Net actuarial (loss) gain	(30)	35	(38)
Net prior service credits arising during the period	0	0	9
Less: Amortization of actuarial loss, included in net loss	(1)	3	10
Net unrecognized net periodic pension and other postretirement benefits	(31)	38	(19)
Other comprehensive (loss) income	31	35	(31)
Comprehensive (loss)	$ 7,408	$ (1,171)	$ (2,026)