Supplementary Consolidated Financial Statement Schedule Valuation And Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2013
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 134	[1]	$ 136	[1]	$ 125
Charged to Costs and Expense	75		36		32
Charged to Other Accounts	0	[2]	(1)	[2]	17	[2]
Deductions From Allowance Accounts	(35)	[3]	(37)	[3]	(38)	[3]
Balance at End of Year	174	[1]	134	[1]	136	[1]
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	112	[1]	121	[1]	111
Charged to Costs and Expense	67		36		28
Charged to Other Accounts	0	[2]	(11)	[2]	16	[2]
Deductions From Allowance Accounts	(38)	[3]	(34)	[3]	(34)	[3]
Balance at End of Year	141	[1]	112	[1]	121	[1]
Other Allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	22	[1]	15	[1]	14
Charged to Costs and Expense	8		0		4
Charged to Other Accounts	0	[2]	10	[2]	1	[2]
Deductions From Allowance Accounts	3	[3]	(3)	[3]	(4)	[3]
Balance at End of Year	33	[1]	22	[1]	15	[1]
Written Off [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Deductions From Allowance Accounts	(34)		(39)		(38)
Credited To Other Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Deductions From Allowance Accounts	(1)		2		0
Amounts Shown As Deductions From Current And Non-Current Receivables [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at End of Year	$ 174		$ 134		$ 136

[1] Amounts shown as deductions from current and non - current receivables [$0], $136, $125.

[2] Primarily represents reclassifications from other balance sheet accounts.

[3] Deductions:Written off - [($0)], ($38), ($44)Credited to other accounts - [($0)], ($0), ($6)Total - [($0)], ($38), ($50)