Stockholders' Equity (Share-based Compensation Expense) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 2,742,000	$ 2,962,000	$ 8,568,000	$ 5,672,000
Employee Stock Option
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	2,142,000	2,651,000	7,751,000	5,030,000
Employee Stock Option | Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	250,000	267,000	897,000	503,000
Employee Stock Option | General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	1,892,000	2,384,000	6,854,000	4,527,000
Restricted Stock | Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	7,000	12,000	51,000	23,000
Restricted Stock | General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	593,000	46,000	714,000	86,000
Restricted Stock Units (RSUs) | Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	47	0	157	0
Restricted Stock Units (RSUs) | General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 0	$ 253,000	$ 52,000	$ 533,000