Derivative instruments Derivative Instruments (Details) (Cash flow hedge [Member], Cross currency swap contracts [Member]) In Millions, unless otherwise specified	Sep. 30, 2012 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member] USD ($)	Sep. 30, 2012 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member] EUR (€)	Sep. 30, 2012 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member] USD ($)	Sep. 30, 2012 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member] GBP (£)	Sep. 30, 2012 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member] USD ($)	Sep. 30, 2012 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member] GBP (£)	Sep. 30, 2012 Interest rate paid [Member] 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member]	Sep. 30, 2012 Interest rate paid [Member] 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]	Sep. 30, 2012 Interest rate paid [Member] 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member]	Sep. 30, 2012 Interest rate received [Member] 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member]	Sep. 30, 2012 Interest rate received [Member] 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]	Sep. 30, 2012 Interest rate received [Member] 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member]
Derivative [Line Items]
Notional Amount	$ 864	€ 675	$ 748	£ 475	$ 1,122	£ 700
Fixed Interest Rate							2.60%	5.80%	4.30%	2.125%	5.50%	4.00%