Collaborative arrangements (Details Textual 1) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Product sales	$ 3,907	$ 3,877	$ 3,893	$ 3,618	$ 3,760	$ 3,759	$ 3,613	$ 3,528	$ 15,295	$ 14,660	$ 14,351
Collaborative Arrangement with Glaxo Group Limited [Member] | Primary Territories [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Product sales									62	5
Collaborative Arrangement with Glaxo Group Limited [Member] | Selling, General and Administrative [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Cost recoveries									30	46	29
Collaborative Arrangement with Glaxo Group Limited [Member] | Other revenues [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received										75
Milestone payments received and deferred [Member] | Collaborative Arrangement with Glaxo Group Limited [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received											$ 45
Milestone payments received and deferred [Member] | Collaborative Arrangement with Glaxo Group Limited [Member] | Other revenues [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Amortization period of payments received and deferred under collaborative arrangements, in years											13 years