Supplementary Consolidated Financial Statement Schedule Valuation And Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2012
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 136	[1]	$ 125	[1]	$ 140
Charged to Costs and Expense	38		32		35
Charged to Other Accounts	(1)	[2]	17	[2]	0	[2]
Deductions From Allowance Accounts	(37)	[3]	(38)	[3]	(50)	[3]
Balance at End of Year	136	[1]	136	[1]	125	[1]
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	121	[1]	111	[1]	124
Charged to Costs and Expense	38		28		30
Charged to Other Accounts	(12)	[2]	16	[2]	0	[2]
Deductions From Allowance Accounts	(34)	[3]	(34)	[3]	(43)	[3]
Balance at End of Year	113	[1]	121	[1]	111	[1]
Other Allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	15	[1]	14	[1]	16
Charged to Costs and Expense	0		4		5
Charged to Other Accounts	11	[2]	1	[2]	0	[2]
Deductions From Allowance Accounts	(3)	[3]	(4)	[3]	(7)	[3]
Balance at End of Year	23	[1]	15	[1]	14	[1]
Written Off [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Deductions From Allowance Accounts	(39)		(38)		(44)
Credited To Other Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Deductions From Allowance Accounts	2		0		(6)
Amounts Shown As Deductions From Current And Non-Current Receivables [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at End of Year	$ 136		$ 136		$ 125

[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)