Collaborative arrangements (Textuals 2) (Details) (Astrazeneca Plc. [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of related development costs for the 2012-2014 period that were funded by partner	65.00%
Other revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments received			$ 50
Research and development expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost recoveries	$ 110	$ 194	$ 28