Basis of Presentation (Accounting for Share-Based Compensation) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basis of Presentation [Line Items]
Share-based compensation expense total	$ 1,533	$ 1,013	$ 4,149	$ 3,116
Research and development expense [Member]
Basis of Presentation [Line Items]
Share-based compensation expense total	438	263	1,272	1,211
General and administrative expenses [Member]
Basis of Presentation [Line Items]
Share-based compensation expense total	$ 1,095	$ 750	$ 2,877	$ 1,905