Stockholders' Equity (Summary of Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Options
Outstanding Options, Beginning of period	12,240,467
Options granted	2,225,900
Options exercised	(9,200)
Options cancelled	(15,235)
Options expired	(105,693)
Outstanding Options, End of period	14,336,239
Exercisable at the end of period	7,896,359
Weighted-Average Exercise Price
Outstanding Exercise Price (in dollars per share)	$ 15.41
Options granted (in dollars per share)	11.85
Options exercised (in dollars per share)	11.31
Options cancelled (in dollars per share)	14.03
Options expired (in dollars per share)	24.12
Outstanding Exercise Price (in dollars per share)	14.80
Exercisable at the end of period	$ 16.10
Additional Disclosures
Outstanding Contractual Term (in Years)	4 years 10 months 21 days
Outstanding Intrinsic Value	$ 3,670
Exercisable at the end of period (in Years)	3 years 5 months 9 days
Exercisable aggregate intrinsic value	$ 2,024
Allocated share base compensation	3,851	$ 2,230
Employee Stock Option
Additional Disclosures
Allocated share base compensation	$ 2,100	$ 1,600