Lease Obligations (Narrative) (Details) (USD $)	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Operating Leased Assets [Line Items]
Rental expense	$ 240,000,000	$ 157,000,000	$ 154,000,000
Property leases term (years)	P5Y
Equipment Lease [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Lease term (years)	P3Y
Equipment Lease [Member] | Minimum [Member]
Operating Leased Assets [Line Items]
Lease term (years)	P1Y
Facilities Lease [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Lease term (years)	P7Y
Facilities Lease [Member] | Minimum [Member]
Operating Leased Assets [Line Items]
Lease term (years)	P1Y