Collaborative arrangements (Details Textual) (Collaborative arrangement with AstraZeneca PLC [Member], USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of related development costs for the 2012-2014 periods will be funded by partner	65.00%
Ratio of development cost sharing after 2014	the companies will share costs equally
Ratio of profits and losses shared with partner	profits and losses related to the collaboration would be shared equally
Other revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments received	50