Severance and Exit Costs 1 (Details) (USD $) In Millions, unless otherwise specified					9 Months Ended
	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2012 Severance [Member]	Dec. 31, 2011 Severance [Member]	Dec. 31, 2012 Facility Abandonment [Member]	Dec. 31, 2011 Facility Abandonment [Member]
Restructuring Reserve [Roll Forward]
Accrued beginning balance	$ 45	$ 53	$ 61	$ 55	$ 13	$ 8	$ 40	$ 47
Expense					18	49	0	0
Change in estimate					(3)	(6)	0	0
Payments					(8)	(30)	(11)	(8)
Accretion and other					0	0	(4)	1
Accrued ending balance	$ 45	$ 53	$ 61	$ 55	$ 20	$ 21	$ 25	$ 40