CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (1,206)	$ (1,995)	$ (3,345)
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustment	(1)	(11)	(25)
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(2)	0	0
Net unrealized holding (losses) gains on securities	0	(1)	(6)
Unrecognized net periodic pension and other postretirement benefits:
Net actuarial (loss) gain	35	(38)	(393)
Net prior service credits arising during the period	0	9	0
Less: Amortization of actuarial loss, included in net loss	3	10	0
Less: Settlement event charge, included in net loss	0	0	59
Net unrecognized net periodic pension and other postretirement benefits	38	(19)	(334)
Other comprehensive (loss) income	35	(31)	(365)
Comprehensive (loss)	$ (1,171)	$ (2,026)	$ (3,710)