Derivative instruments (Cross-currency Swaps) (Details) - Cash flow hedge [Member] - Cross currency swap contracts [Member] € in Millions, £ in Millions, SFr in Millions, $ in Millions	Jun. 30, 2017 USD ($)	Jun. 30, 2017 EUR (€)	Jun. 30, 2017 CHF (SFr)	Jun. 30, 2017 GBP (£)
2.125% Euro Notes Due 2019 [Member]
Derivative [Line Items]
Notional amount	$ 864	€ 675
1.25% 2022 euro Notes [Member]
Derivative [Line Items]
Notional amount	1,388	1,250
0.41% Swiss-franc-denominated bonds due 2023 (0.41% 2023 Swiss franc Bonds) [Member]
Derivative [Line Items]
Notional amount	704		SFr 700
2.00% €750 million notes due 2026 (2.00% 2026 euro Notes) [Member]
Derivative [Line Items]
Notional amount	833	€ 750
5.50% pound-sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]
Derivative [Line Items]
Notional amount	747			£ 475
4.00% pound-sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member]
Derivative [Line Items]
Notional amount	$ 1,111			£ 700
Euro Member Countries, Euro | 2.125% Euro Notes Due 2019 [Member]
Derivative [Line Items]
Interest rate	2.125%	2.125%	2.125%	2.125%
Euro Member Countries, Euro | 1.25% 2022 euro Notes [Member]
Derivative [Line Items]
Interest rate	1.25%	1.25%	1.25%	1.25%
Euro Member Countries, Euro | 2.00% €750 million notes due 2026 (2.00% 2026 euro Notes) [Member]
Derivative [Line Items]
Interest rate	2.00%	2.00%	2.00%	2.00%
United States of America, Dollars | 2.125% Euro Notes Due 2019 [Member]
Derivative [Line Items]
Interest rate	2.60%	2.60%	2.60%	2.60%
United States of America, Dollars | 1.25% 2022 euro Notes [Member]
Derivative [Line Items]
Interest rate	3.20%	3.20%	3.20%	3.20%
United States of America, Dollars | 0.41% Swiss-franc-denominated bonds due 2023 (0.41% 2023 Swiss franc Bonds) [Member]
Derivative [Line Items]
Interest rate	3.40%	3.40%	3.40%	3.40%
United States of America, Dollars | 2.00% €750 million notes due 2026 (2.00% 2026 euro Notes) [Member]
Derivative [Line Items]
Interest rate	3.90%	3.90%	3.90%	3.90%
United States of America, Dollars | 5.50% pound-sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]
Derivative [Line Items]
Interest rate	6.00%	6.00%	6.00%	6.00%
United States of America, Dollars | 4.00% pound-sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member]
Derivative [Line Items]
Interest rate	4.50%	4.50%	4.50%	4.50%
Switzerland, Francs | 0.41% Swiss-franc-denominated bonds due 2023 (0.41% 2023 Swiss franc Bonds) [Member]
Derivative [Line Items]
Interest rate	0.41%	0.41%	0.41%	0.41%
United Kingdom, Pounds | 5.50% pound-sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]
Derivative [Line Items]
Interest rate	5.50%	5.50%	5.50%	5.50%
United Kingdom, Pounds | 4.00% pound-sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member]
Derivative [Line Items]
Interest rate	4.00%	4.00%	4.00%	4.00%