Debt (Maturities) (Details) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Other debt due in the fiscal years ending:
2014	$ 40,709,000,000
2015	9,427,000,000
2016	10,739,000,000
2017	4,608,000,000
2018	7,197,000,000
Thereafter	6,152,000,000
Total debt	78,832,000,000	73,234,000,000
Interest payments	$ 1,300,000,000	$ 1,600,000,000	$ 1,700,000,000