Derivative instruments (Cross-currency Swaps) (Details) - Cash flow hedge - Cross-currency swap contracts € in Millions, £ in Millions, SFr in Millions, $ in Millions	Sep. 30, 2022 USD ($)	Sep. 30, 2022 CHF (SFr)	Sep. 30, 2022 EUR (€)	Sep. 30, 2022 GBP (£)
0.41% 2023 Swiss franc Bonds
Derivative [Line Items]
Notional amounts	$ 704	SFr 700
2.00% 2026 euro Notes
Derivative [Line Items]
Notional amounts	833		€ 750
5.50% 2026 pound sterling Notes
Derivative [Line Items]
Notional amounts	747			£ 475
4.00% 2029 pound sterling Notes
Derivative [Line Items]
Notional amounts	$ 1,111			£ 700
Euro Member Countries, Euro | 2.00% 2026 euro Notes
Derivative [Line Items]
Interest rates	2.00%	2.00%	2.00%	2.00%
Switzerland, Francs | 0.41% 2023 Swiss franc Bonds
Derivative [Line Items]
Interest rates	0.40%	0.40%	0.40%	0.40%
United Kingdom, Pounds | 5.50% 2026 pound sterling Notes
Derivative [Line Items]
Interest rates	5.50%	5.50%	5.50%	5.50%
United Kingdom, Pounds | 4.00% 2029 pound sterling Notes
Derivative [Line Items]
Interest rates	4.00%	4.00%	4.00%	4.00%
United States of America, Dollars | 0.41% 2023 Swiss franc Bonds
Derivative [Line Items]
Interest rates	3.40%	3.40%	3.40%	3.40%
United States of America, Dollars | 2.00% 2026 euro Notes
Derivative [Line Items]
Interest rates	3.90%	3.90%	3.90%	3.90%
United States of America, Dollars | 5.50% 2026 pound sterling Notes
Derivative [Line Items]
Interest rates	6.00%	6.00%	6.00%	6.00%
United States of America, Dollars | 4.00% 2029 pound sterling Notes
Derivative [Line Items]
Interest rates	4.60%	4.60%	4.60%	4.60%