Debt (Details) (USD $)	3 Months Ended		6 Months Ended																					0 Months Ended											6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011	Sep. 30, 2011	Mar. 31, 2012 Senior Notes Sept 2014 [Member]	Sep. 30, 2011 Senior Notes Sept 2014 [Member]	Mar. 31, 2012 Senior Notes Feb 2015 [Member]	Sep. 30, 2011 Senior Notes Feb 2015 [Member]	Mar. 31, 2012 Senior Notes Sept 2015 [Member]	Sep. 30, 2011 Senior Notes Sept 2015 [Member]	Mar. 31, 2012 Senior Notes April 2016 [Member]	Sep. 30, 2011 Senior Notes April 2016 [Member]	Mar. 31, 2012 Senior Notes October 2017 [Member]	Sep. 30, 2011 Senior Notes October 2017 [Member]	Mar. 31, 2012 Senior Notes Sept 2019 [Member]	Sep. 30, 2011 Senior Notes Sept 2019 [Member]	Mar. 31, 2012 Senior Notes March 2021 [Member]	Sep. 30, 2011 Senior Notes March 2021 [Member]	Mar. 31, 2012 Senior Debentures April 2036 [Member]	Sep. 30, 2011 Senior Debentures April 2036 [Member]	Mar. 31, 2012 Senior Debentures Oct 2037 [Member]	Sep. 30, 2011 Senior Debentures Oct 2037 [Member]	Jan. 09, 2012 Senior Debentures Dec 2055 [Member]	Mar. 31, 2012 Senior Debentures Dec 2055 [Member]	Sep. 30, 2011 Senior Debentures Dec 2055 [Member]	Mar. 31, 2012 Senior Notes April 2017 [Member]	Sep. 30, 2011 Senior Notes April 2017 [Member]	Mar. 31, 2012 Senior Notes Dec 2016 [Member]	Sep. 30, 2011 Senior Notes Dec 2016 [Member]	Mar. 31, 2012 Senior Notes Dec 2021 [Member]	Sep. 30, 2011 Senior Notes Dec 2021 [Member]	Mar. 31, 2012 Senior Debentures due Feb 2042 [Member]	Sep. 30, 2011 Senior Debentures due Feb 2042 [Member]	Mar. 31, 2012 Revolving Credit Agreement [Member]	Mar. 31, 2012 Bank Credit Facilities [Member] indays
Debt Instrument [Line Items]
Senior notes and debentures						$ 598,000,000	$ 597,000,000	$ 499,000,000	$ 0	$ 250,000,000	$ 250,000,000	$ 916,000,000	$ 916,000,000	$ 498,000,000	$ 498,000,000	$ 553,000,000	$ 553,000,000	$ 492,000,000	$ 492,000,000	$ 1,736,000,000	$ 1,736,000,000	$ 248,000,000	$ 248,000,000		$ 0	$ 750,000,000	$ 496,000,000	$ 496,000,000	$ 398,000,000	$ 0	$ 590,000,000	$ 0	$ 245,000,000	$ 0
Total Senior Debt Issued			1,750,000,000
Coupon rate						4.375%		1.25%		4.25%		6.25%		6.125%		5.625%		4.50%		6.875%		6.75%			6.85%		3.50%		2.50%		3.875%		4.50%
Commercial paper - amount outstanding	0		0		423,000,000
Capital lease and other obligations	259,000,000		259,000,000		406,000,000
Total Debt	7,778,000,000		7,778,000,000		7,365,000,000
Less current portion	(21,000,000)		(21,000,000)		(23,000,000)
Total noncurrent portion	7,757,000,000		7,757,000,000		7,342,000,000
Principal amount of senior notes								500,000,000																					400,000,000		600,000,000		250,000,000
Rate premium discount senior debt								99.789%																					99.366%		98.361%		98.063%
Senior Notes And Debentures [Abstract]
Fair Value of Company's senior notes and debentures	1,100,000,000		1,100,000,000
Senior debt redeemed																								750,000,000
Loss on extinguishment of debt	(21,000,000)	(87,000,000)	(21,000,000)	(87,000,000)
Redemption Price Percentage																								100.00%
Line Of Credit Facility Abstract
Total Credit Facility Capacity																																			2,100,000,000	600,000,000
Minimum Interest Coverage Ratio																																			Company’s interest coverage for the most recent four consecutive fiscal quarters to be at least 3.0x
Credit facility margin rate minimum																																			0.50%
Credit facility margin rate maximum																																			1.50%
Unamortized net discount related to senior notes and debentures	49,000,000		49,000,000
Former Credit Facility Borrowing Capacity																																			$ 2,000,000,000
Contractual term of the credit facilities																																				364