Related party transactions (Details Textual) (Kirin-Amgen [Member], USD $)	12 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013 Selling, General and Administrative [Member]	Dec. 31, 2012 Selling, General and Administrative [Member]	Dec. 31, 2011 Selling, General and Administrative [Member]	Dec. 31, 2013 Cost of Sales [Member]	Dec. 31, 2012 Cost of Sales [Member]	Dec. 31, 2011 Cost of Sales [Member]	Dec. 31, 2013 Other Revenues [Member]	Dec. 31, 2012 Other Revenues [Member]	Dec. 31, 2011 Other Revenues [Member]	Dec. 31, 2013 Research and Development Expense [Member]	Dec. 31, 2012 Research and Development Expense [Member]	Dec. 31, 2011 Research and Development Expense [Member]	Dec. 31, 2013 Noncurrent Other Assets [Member]	Dec. 31, 2012 Noncurrent Other Assets [Member]	Dec. 31, 2013 Other Current Assets [Member]	Dec. 31, 2012 Accrued Liabilities [Member]
Related Party Transaction [Line Items]
Ownership interest (in percent) in related party	50.00%	50.00%	50.00%
Company's share of profits (losses) of related party				$ (6,000,000)	$ (24,000,000)	$ 47,000,000
Approximate carrying value of the company's equity method investment net of dividends received																300,000,000	400,000,000
Royalties earned by related party from Amgen							272,000,000	274,000,000	298,000,000
Revenues earned by Amgen from related party										117,000,000	115,000,000	130,000,000
Payments that may be received upon the achievement of various substantive success-based development and regulatory approval milestones	85,000,000
Cost recoveries by Amgen from related party													218,000,000	142,000,000	85,000,000
Amount due from related party																		22,000,000
Amount owed to related party																			$ 31,000,000