Debt and Financing Activities (Long-Term Debt) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended				12 Months Ended						1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended		12 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended	0 Months Ended	12 Months Ended		2 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 D	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 05, 2014 Floating Rate Notes Due September 10, 2015 [Member]	Mar. 31, 2014 1.29 % Notes Due March 10, 2017 [Member]	Mar. 31, 2013 1.29 % Notes Due March 10, 2017 [Member]	Mar. 05, 2014 1.29 % Notes Due March 10, 2017 [Member]	Mar. 05, 2014 2.28% Notes Due March 15, 2019 [Member]	Mar. 05, 2014 3.80% Notes Due March 15, 2024 [Member]	Mar. 05, 2014 4.88 % Notes Due March 15, 2044 [Member]	Mar. 31, 2013 1.40% Notes Due March 15, 2018 [Member]	Mar. 31, 2014 1.40% Notes Due March 15, 2018 [Member]	Mar. 31, 2013 1.40% Notes Due March 15, 2018 [Member]	Mar. 08, 2013 1.40% Notes Due March 15, 2018 [Member]	Mar. 31, 2013 2.85% Notes Due March 15, 2023 [Member]	Mar. 31, 2014 2.85% Notes Due March 15, 2023 [Member]	Mar. 31, 2013 2.85% Notes Due March 15, 2023 [Member]	Mar. 08, 2013 2.85% Notes Due March 15, 2023 [Member]	Mar. 31, 2013 1.40% Notes Due March 15, 2018 And 2.85% Notes Due March 15, 2023 [Member]	Dec. 31, 2012 0.95% Notes Due December 4, 2015 [Member]	Mar. 31, 2014 0.95% Notes Due December 4, 2015 [Member]	Mar. 31, 2013 0.95% Notes Due December 4, 2015 [Member]	Dec. 04, 2012 0.95% Notes Due December 4, 2015 [Member]	Dec. 31, 2012 2.70% Notes Due December 15, 2022 [Member]	Mar. 31, 2014 2.70% Notes Due December 15, 2022 [Member]	Mar. 31, 2013 2.70% Notes Due December 15, 2022 [Member]	Dec. 04, 2012 2.70% Notes Due December 15, 2022 [Member]	Dec. 31, 2012 0.95% Notes Due December 4, 2015 And 2.70% Notes Due December 15, 2022 [Member]	Feb. 15, 2014 6.50% Notes Due February 15, 2014 [Member]	Mar. 31, 2014 6.50% Notes Due February 15, 2014 [Member]	Mar. 31, 2013 6.50% Notes Due February 15, 2014 [Member]	Mar. 01, 2013 Five Point Two Five Percent Notes Due March One Two Thousand Thirteen [Member]	Mar. 31, 2014 London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date							Mar. 10, 2017	Mar. 10, 2017					Mar. 15, 2018	Mar. 15, 2018	Mar. 15, 2018		Mar. 15, 2023	Mar. 15, 2023	Mar. 15, 2023			Dec. 04, 2015	Dec. 04, 2015	Dec. 04, 2015		Dec. 15, 2022	Dec. 15, 2022	Dec. 15, 2022				Feb. 15, 2014	Feb. 15, 2014
Debt Instrument, Face Amount						$ 400			$ 700	$ 1,100	$ 1,100	$ 800				$ 500				$ 400					$ 500				$ 400
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	0.64%	0.64%	0.64%																																0.40%
Debt Instrument, Date of First Required Payment																					Sep. 15, 2013	Jun. 04, 2013				Jun. 15, 2013
Proceeds from issuances of long-term debt	4,068		4,114	1,798	0																891									892
Number Of Days Notice Before Notes Can Be Redeemed		30
Contingent purchase offer, Series		101.00%
Repayments of Other Short-term Debt																															350
Amount repaid																																		500
Future principal payments of long-term debt in 2015	1,424	1,424	1,424
Future principal payments of long-term debt in 2016	1,535	1,535	1,535
Future principal payments of long-term debt in 2017	1,277	1,277	1,277
Future principal payments of long-term debt in 2018	520	520	520
Future principal payments of long-term debt in 2019	1,485	1,485	1,485
Future principal payments of long-term debt, thereafter	$ 4,132	$ 4,132	$ 4,132
Interest rate on debt							1.29%	1.29%	1.29%	2.28%	3.80%	4.88%	1.40%	1.40%	1.40%	1.40%	2.85%	2.85%	2.85%	2.85%			0.95%	0.95%	0.95%		2.70%	2.70%	2.70%		6.50%	6.50%	6.50%	5.25%