Fair value measurement (Details Textual) (USD $)	12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Biovex Group Inc [Member] ContingentConsideration	Mar. 04, 2011 Biovex Group Inc [Member]	Dec. 31, 2012 Other Operating Expense [Member]	Dec. 31, 2012 Corporate Debt Securities [Member]	Dec. 31, 2012 Other government-related debt securities [Member]
Fair Value Measurement (Textual) [Abstract]
Investment maturity period						5 years	5 years
Length of time hedged in foreign currency contracts	three years
Maximum additional consideration due contingent on certain milestones			$ 575,000,000	$ 575,000,000
Maximum number of contingent consideration payments for achieving regulatory and sales related milestones			8
The number of payments that will potentially be made that each equal the largest potential contingent consideration payment			3
Largest potential contingent consideration payments			125,000,000
Change in fair values of contingent consideration obligations					31,000,000
Aggregate fair value of long-term debt, including current portion	29,900,000,000	23,000,000,000
Carrying value of long-term debt, including current portion	$ 26,529,000,000	$ 21,428,000,000