Stock Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Weighted Average Grant Price [Roll Forward]
Expense resulting from modifications to stock options	$ 500,000
Fair value and assumptions used in determining fair value of stock options [Abstract]
Volatility (in hundredths)	96.20%	111.60%
Risk-free interest rate (in hundredths)	0.70%	0.90%
Dividend yield (in hundredths)	0.00%	0.00%
Expected option term	6 years 3 months	6 years 3 months
Weighted-average fair value of stock options granted (in dollars per share)	$ 3.21	$ 2.68
Number of Shares [Roll Forward]
Options outstanding (in shares)	891,751	214,275	259,275
Granted (in shares)	1,116,384	766,000	0
Exercised (in shares)	(30,250)	(5,200)	0
Cancelled (in shares)	(160,046)	(83,324)	(45,000)
Options outstanding (in shares)	1,817,839	891,751	214,275
Vested and expected to vest (in shares)	1,692,915	816,414	214,275
Exercisable (in shares)	438,145	125,751	214,275
Weighted Average Exercise Price [Roll Forward]
Options outstanding (in dollars per share)	$ 5.15	$ 18.43	$ 23
Granted (in dollars per share)	$ 4.12	$ 3.77	$ 0
Exercised (in dollars per share)	$ 7.08	$ 6.16	$ 0
Cancelled (in dollars per share)	$ 9.54	$ 26.57	$ 48.04
Options outstanding (in dollars per share)	$ 4.10	$ 5.15	$ 18.43
Vested and expected to vest (in dollars per share)	$ 4.11	$ 5.30	$ 18.43
Exercisable (in dollars per share)	$ 4.59	$ 13.54	$ 18.43
Weighted Average Remaining Contractual Life in Years [Abstract]
Options outstanding	7 years 10 months 2 days
Vested and expected to vest	7 years 8 months 16 days
Exercisable	2 years 5 months 5 days
Aggregate Intrinsic Value [Abstract]
Options outstanding	4,790,817
Vested and expected to vest	4,457,650
Exercisable	1,003,740
Total intrinsic value of stock options exercised during the period	24,590,000	23,482,000
Unrecognized compensation expense related to unvested stock options	5,900,000
Restricted Stock and Restricted Stock Units [Abstract]
Number of periods that noncash compensation expense is recognized	2 years
Number of common shares to be received in lieu of per RS and RSU (in shares)	1,400,000
Restricted Stock or Unit Expense	1,200,000
$3.03 to $3.13 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.03
Range of Exercise Prices upper range limit (in dollars per share)	$ 3.13
Number of Options outstanding (in shares)	482,305
Weighted Average Remaining Contractual Term (in Years)	6 years 4 months 6 days
Weighted Average Exercise Price (in dollars per share)	$ 3.03
Number of Options exercisable (in shares)	234,495
Weighted Average Exercise Price (in dollars per share)	$ 3.03
$3.14 to $3.39 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.14
Range of Exercise Prices upper range limit (in dollars per share)	$ 3.39
Number of Options outstanding (in shares)	21,400
Weighted Average Remaining Contractual Term (in Years)	9 years 5 months 8 days
Weighted Average Exercise Price (in dollars per share)	$ 3.24
Number of Options exercisable (in shares)	0
Weighted Average Exercise Price (in dollars per share)	$ 0
$3.40 to $3.47 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.4
Range of Exercise Prices upper range limit (in dollars per share)	$ 3.47
Number of Options outstanding (in shares)	708,314
Weighted Average Remaining Contractual Term (in Years)	9 years 8 months 8 days
Weighted Average Exercise Price (in dollars per share)	$ 3.4
Number of Options exercisable (in shares)	0
Weighted Average Exercise Price (in dollars per share)	$ 0
$3.48 to $4.05 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.48
Range of Exercise Prices upper range limit (in dollars per share)	$ 4.05
Number of Options outstanding (in shares)	16,500
Weighted Average Remaining Contractual Term (in Years)	9 years 6 months 4 days
Weighted Average Exercise Price (in dollars per share)	$ 3.69
Number of Options exercisable (in shares)	0
Weighted Average Exercise Price (in dollars per share)	$ 0
$4.55 to $4.96 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 4.55
Range of Exercise Prices upper range limit (in dollars per share)	$ 4.96
Number of Options outstanding (in shares)	186,170
Weighted Average Remaining Contractual Term (in Years)	9 years 8 months 26 days
Weighted Average Exercise Price (in dollars per share)	$ 4.55
Number of Options exercisable (in shares)	0
Weighted Average Exercise Price (in dollars per share)	$ 0
$4.97 to $5.89 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 4.97
Range of Exercise Prices upper range limit (in dollars per share)	$ 5.89
Number of Options outstanding (in shares)	4,000
Weighted Average Remaining Contractual Term (in Years)	9 years 9 months 0 days
Weighted Average Exercise Price (in dollars per share)	$ 4.97
Number of Options exercisable (in shares)	0
Weighted Average Exercise Price (in dollars per share)	$ 0
$5.90 to $6.33 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 5.9
Range of Exercise Prices upper range limit (in dollars per share)	$ 6.33
Number of Options outstanding (in shares)	198,400
Weighted Average Remaining Contractual Term (in Years)	1 year 7 months 28 days
Weighted Average Exercise Price (in dollars per share)	$ 5.9
Number of Options exercisable (in shares)	182,900
Weighted Average Exercise Price (in dollars per share)	$ 5.9
$6.34 to $8.29 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 6.34
Range of Exercise Prices upper range limit (in dollars per share)	$ 8.29
Number of Options outstanding (in shares)	185,250
Weighted Average Remaining Contractual Term (in Years)	9 years 7 months 20 days
Weighted Average Exercise Price (in dollars per share)	$ 6.64
Number of Options exercisable (in shares)	5,250
Weighted Average Exercise Price (in dollars per share)	$ 6.5
$8.30 to $17.59 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 8.3
Range of Exercise Prices upper range limit (in dollars per share)	$ 17.59
Number of Options outstanding (in shares)	10,250
Weighted Average Remaining Contractual Term (in Years)	9 months 18 days
Weighted Average Exercise Price (in dollars per share)	$ 9.18
Number of Options exercisable (in shares)	10,250
Weighted Average Exercise Price (in dollars per share)	$ 9.18
$17.60 to $17.60 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices lower range limit (in dollars per share)	$ 17.6
Range of Exercise Prices upper range limit (in dollars per share)	$ 17.6
Number of Options outstanding (in shares)	5,250
Weighted Average Remaining Contractual Term (in Years)	4 months 10 days
Weighted Average Exercise Price (in dollars per share)	$ 17.6
Number of Options exercisable (in shares)	5,250
Weighted Average Exercise Price (in dollars per share)	$ 17.6
2000 Plan [Member]
Weighted Average Grant Price [Roll Forward]
Number of equity compensation plans	2
Number of additional shares authorized for current and future use (in shares)		3,000,000
Value of shares that can be purchased under the plan per year	225,000,000,000
Reserved for future issuance maximum shares of common stock (in shares)	3,925,000
Shares available for grant (in shares)	737,448
2000 ESPP [Member]
Weighted Average Grant Price [Roll Forward]
Reserved for future issuance maximum shares of common stock (in shares)	150,000
Shares available for grant (in shares)	150,000
Stock Options [Member]
Weighted Average Grant Price [Roll Forward]
Allocated share-based compensation expense	1,800,000	300,000	400,000
Expected weighted average period for recognizing unrecognized compensation expense	3 years 6 months 22 days
Aggregate Intrinsic Value [Abstract]
Expected weighted average period for recognizing unrecognized compensation expense	3 years 6 months 22 days
Stock Options [Member] | General and Administrative Expense [Member]
Weighted Average Grant Price [Roll Forward]
Allocated share-based compensation expense	1,500,000	200,000	0
Stock Options [Member] | Research and Development Expense [Member]
Weighted Average Grant Price [Roll Forward]
Allocated share-based compensation expense	300,000	100,000	0
Restricted Stock (RS) [Member]
Number of Non Option Outstanding [Roll Forward]
Outstanding, beginning balance (in shares)			8,772
Granted (in shares)			30,270
Released (in shares)			(39,042)
Weighted Average Grant Price [Roll Forward]
Outstanding weighted average grant price (in dollars per share)			$ 17.1
Granted (in dollars per share)			$ 8.80
Released (in dollars per share)			$ 10.72
Restricted Stock Units (RSUs) [Member]
Number of Non Option Outstanding [Roll Forward]
Outstanding, beginning balance (in shares)	487,025
Granted (in shares)	61,011	491,255
Released (in shares)	(322,819)
Forfeited (in shares)	(9,692)	(4,230)
Outstanding, ending balance (in shares)	215,525	487,025
Expected to Vest (in shares)	206,395
Weighted Average Grant Price [Roll Forward]
Outstanding weighted average grant price (in dollars per share)	$ 6.37
Granted (in dollars per share)	$ 3.44	$ 6.36
Released (in dollars per share)	$ 4.59
Forfeited (in dollars per share)	$ 5.69	$ 5.13
Outstanding weighted average grant price (in dollars per share)	$ 6.26	$ 6.37
Expected to Vest (in dollars per share)	$ 6.23
Restricted Stock and Restricted Stock Units [Member]
Weighted Average Grant Price [Roll Forward]
Allocated share-based compensation expense	1,200,000	1,300,000	300,000
Expected weighted average period for recognizing unrecognized compensation expense	10 months 24 days
Aggregate Intrinsic Value [Abstract]
Expected weighted average period for recognizing unrecognized compensation expense	10 months 24 days
Restricted Stock and Restricted Stock Units [Abstract]
Unrecognized compensation expense related to unvested RSU's	600,000
Restricted Stock and Restricted Stock Units [Member] | General and Administrative Expense [Member]
Weighted Average Grant Price [Roll Forward]
Allocated share-based compensation expense	800,000	900,000	200,000
Restricted Stock and Restricted Stock Units [Member] | Research and Development Expense [Member]
Weighted Average Grant Price [Roll Forward]
Allocated share-based compensation expense	$ 500,000	$ 400,000	$ 100,000