Debt And Financing Activities (Schedule Of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended			12 Months Ended		1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended			12 Months Ended				1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended			12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 5.25% Notes Due March 1, 2013 [Member]	Mar. 31, 2012 5.25% Notes Due March 1, 2013 [Member]	Mar. 01, 2013 5.25% Notes Due March 1, 2013 [Member]	Mar. 31, 2013 6.50% Notes Due February 15, 2014 [Member]	Mar. 31, 2012 6.50% Notes Due February 15, 2014 [Member]	Dec. 31, 2012 0.95% Notes Due December 4, 2015 [Member]	Mar. 31, 2013 0.95% Notes Due December 4, 2015 [Member]	Mar. 31, 2012 0.95% Notes Due December 4, 2015 [Member]	Dec. 04, 2012 0.95% Notes Due December 4, 2015 [Member]	Feb. 28, 2011 3.25% Notes Due March 1, 2016 [Member]	Mar. 31, 2013 3.25% Notes Due March 1, 2016 [Member]	Mar. 31, 2012 3.25% Notes Due March 1, 2016 [Member]	Mar. 31, 2013 5.70% Notes Due March 1, 2017 [Member]	Mar. 31, 2012 5.70% Notes Due March 1, 2017 [Member]	Mar. 31, 2013 1.40% Notes Due March 15, 2018 [Member]	Mar. 31, 2013 1.40% Notes Due March 15, 2018 [Member]	Mar. 31, 2012 1.40% Notes Due March 15, 2018 [Member]	Mar. 08, 2013 1.40% Notes Due March 15, 2018 [Member]	Mar. 31, 2013 7.50% Notes Due February 15, 2019 [Member]	Mar. 31, 2012 7.50% Notes Due February 15, 2019 [Member]	Mar. 31, 2013 4.75% Notes Due March 1, 2021 [Member]	Mar. 31, 2012 4.75% Notes Due March 1, 2021 [Member]	Dec. 31, 2012 2.70% Notes Due December 15, 2022 [Member]	Mar. 31, 2013 2.70% Notes Due December 15, 2022 [Member]	Mar. 31, 2012 2.70% Notes Due December 15, 2022 [Member]	Dec. 04, 2012 2.70% Notes Due December 15, 2022 [Member]	Mar. 31, 2013 2.85% Notes Due March 15, 2023 [Member]	Mar. 31, 2013 2.85% Notes Due March 15, 2023 [Member]	Mar. 31, 2012 2.85% Notes Due March 15, 2023 [Member]	Mar. 08, 2013 2.85% Notes Due March 15, 2023 [Member]	Mar. 31, 2013 7.65% Debentures Due March 1, 2027 [Member]	Mar. 31, 2012 7.65% Debentures Due March 1, 2027 [Member]	Mar. 31, 2013 6.00% Notes Due March 1, 2041 [Member]	Mar. 31, 2012 6.00% Notes Due March 1, 2041 [Member]	Mar. 31, 2013 Other Long Term Debt [Member]	Mar. 31, 2012 Other Long Term Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 4,873	$ 3,580	$ 0	$ 500		$ 350	$ 350		$ 499	$ 0			$ 599	$ 598	$ 500	$ 499	$ 499	$ 499	$ 0		$ 349	$ 349	$ 598	$ 598		$ 400	$ 0		$ 400	$ 400	$ 0		$ 175	$ 175	$ 493	$ 493	$ 11	$ 18
Less current portion	(352)	(508)
Total long-term debt	$ 4,521	$ 3,072
Interest rate on debt			5.25%	5.25%	5.25%	6.50%	6.50%		0.95%	0.95%	0.95%	3.25%	3.25%	3.25%	5.70%	5.70%	1.40%	1.40%	1.40%	1.40%	7.50%	7.50%	4.75%	4.75%		2.70%	2.70%	2.70%	2.85%	2.85%	2.85%	2.85%	7.65%	7.65%	6.00%	6.00%
Debt Instrument, Maturity Date			Mar. 01, 2013	Mar. 01, 2013		Feb. 15, 2014	Feb. 15, 2014	Dec. 04, 2015	Dec. 04, 2015	Dec. 04, 2015		Mar. 01, 2016	Mar. 01, 2016	Mar. 01, 2016	Mar. 01, 2017	Mar. 01, 2017	Mar. 15, 2018	Mar. 15, 2018	Mar. 15, 2018		Feb. 15, 2019	Feb. 15, 2019	Mar. 01, 2021	Mar. 01, 2021	Dec. 15, 2022	Dec. 15, 2022	Dec. 15, 2022		Mar. 15, 2023	Mar. 15, 2023	Mar. 15, 2023		Mar. 01, 2027	Mar. 01, 2027	Mar. 01, 2041	Mar. 01, 2041