Share-Based Payment Arrangements, Allocation of Recognized Period Costs (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total compensation expense recognized	$ 3,546	$ 6,536	$ 6,362
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total compensation expense recognized	2,524	4,568	4,499
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total compensation expense recognized	$ 1,022	$ 1,968	$ 1,863