Stockholders' Equity (Changes in Accumulated Other Comprehensive Income by Component) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance	$ (3)
Other Comprehensive Income (Loss), Net of Tax	(1,989)	83	(70)
Ending balance	(1,713)	(3)
Parent Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance	(3)	(65)
Other comprehensive income (loss) before reclassifications	(1,994)	38
Amounts reclassified to earnings and other	5	45
Other comprehensive income (loss) including portion attributable to NCI, net of tax	(1,989)	83
Other comprehensive income (loss) attributable to NCI, net of tax	(279)	21
Other Comprehensive Income (Loss), Net of Tax	(1,710)	62
Ending balance	(1,713)	(3)
Accumulated Translation Adjustment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance	168	136
Other comprehensive income (loss) before reclassifications	(1,845)	9
Amounts reclassified to earnings and other	(10)	44
Other comprehensive income (loss) including portion attributable to NCI, net of tax	(1,855)	53
Other comprehensive income (loss) attributable to NCI, net of tax	(267)	21
Other Comprehensive Income (Loss), Net of Tax	(1,588)	32
Ending balance	(1,420)	168
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance	(11)	(5)
Other comprehensive income (loss) before reclassifications	(13)	(6)
Amounts reclassified to earnings and other	3	0
Other comprehensive income (loss) including portion attributable to NCI, net of tax	(10)	(6)
Other comprehensive income (loss) attributable to NCI, net of tax	0	0
Other Comprehensive Income (Loss), Net of Tax	(10)	(6)
Ending balance	(21)	(11)
Accumulated Defined Benefit Plans Adjustment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance	(160)	(196)
Other comprehensive income (loss) before reclassifications	(136)	35
Amounts reclassified to earnings and other	12	1
Other comprehensive income (loss) including portion attributable to NCI, net of tax	(124)	36
Other comprehensive income (loss) attributable to NCI, net of tax	(12)	0
Other Comprehensive Income (Loss), Net of Tax	(112)	36
Ending balance	$ (272)	$ (160)