Share-Based Payment Arrangements (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended																																				12 Months Ended												12 Months Ended			12 Months Ended							12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Research and Development [Member]	Dec. 31, 2011 Research and Development [Member]	Dec. 31, 2010 Research and Development [Member]	Dec. 31, 2012 General and Administrative [Member]	Dec. 31, 2011 General and Administrative [Member]	Dec. 31, 2010 General and Administrative [Member]	Dec. 31, 2012 Employees [Member]	Dec. 31, 2011 Employees [Member]	Dec. 31, 2010 Employees [Member]	Dec. 31, 2012 Former CEO [Member]	Dec. 31, 2011 Former CEO [Member]	Dec. 31, 2010 Former CEO [Member]	Dec. 31, 2012 Non Employees [Member]	Dec. 31, 2012 Directors and Officers [Member]	Dec. 31, 2011 Directors and Officers [Member]	Dec. 31, 2010 Directors and Officers [Member]	Dec. 31, 2012 Options [Member]	Dec. 31, 2011 Options [Member]	Dec. 31, 2010 Options [Member]	Dec. 31, 2012 Options [Member] Minimum [Member]	Dec. 31, 2011 Options [Member] Minimum [Member]	Dec. 31, 2010 Options [Member] Minimum [Member]	Dec. 31, 2012 Options [Member] Maximum [Member]	Dec. 31, 2011 Options [Member] Maximum [Member]	Dec. 31, 2010 Options [Member] Maximum [Member]	Dec. 31, 2007 Options [Member] Former CEO [Member]	Dec. 31, 2006 Options [Member] Former CEO [Member]	Dec. 31, 2005 Options [Member] Former CEO [Member]	Dec. 31, 2004 Options [Member] Former CEO [Member]	Dec. 31, 2003 Options [Member] Former CEO [Member]	Dec. 31, 2002 Options [Member] Former CEO [Member]	Dec. 31, 2012 Restricted stock [Member]	Dec. 31, 2010 Restricted stock [Member]	Dec. 31, 2012 Performance-based options [Member]	Dec. 31, 2011 Performance-based options [Member]	Dec. 31, 2010 Performance-based options [Member]	Dec. 31, 2012 1996 Plan and 2005 Plan [Member] Options [Member]	Dec. 31, 2011 1996 Plan and 2005 Plan [Member] Options [Member]	Dec. 31, 2010 1996 Plan and 2005 Plan [Member] Options [Member]	Dec. 31, 2012 1996 Plan and 2005 Plan [Member] Options [Member] Minimum [Member]	Dec. 31, 2012 1996 Plan and 2005 Plan [Member] Options [Member] Maximum [Member]	Dec. 31, 2012 1996 Plan and 2005 Plan [Member] Restricted stock [Member] Minimum [Member]	Dec. 31, 2012 1996 Plan and 2005 Plan [Member] Restricted stock [Member] Maximum [Member]	Dec. 31, 2012 1996 Amended Stock Incentive Plan [Member]	Dec. 31, 2012 2005 Stock Incentive Plan [Member]	Dec. 31, 2011 Qualified Employee Stock Purchase Plan 1998 [Member]	Dec. 31, 2010 Qualified Employee Stock Purchase Plan 1998 [Member]	Dec. 31, 2012 Qualified Employee Stock Purchase Plan 1998 [Member]	Dec. 31, 2011 Qualified Employee Stock Purchase Plan 1998 [Member] Minimum [Member]	Dec. 31, 2010 Qualified Employee Stock Purchase Plan 1998 [Member] Minimum [Member]	Dec. 31, 2011 Qualified Employee Stock Purchase Plan 1998 [Member] Maximum [Member]	Dec. 31, 2010 Qualified Employee Stock Purchase Plan 1998 [Member] Maximum [Member]	Dec. 31, 2011 Non-Qualified Employee Purchase Plan 1998 [Member]	Dec. 31, 2010 Non-Qualified Employee Purchase Plan 1998 [Member]	Dec. 31, 2012 Non-Qualified Employee Purchase Plan 1998 [Member]	Dec. 31, 2011 Non-Qualified Employee Purchase Plan 1998 [Member] Minimum [Member]	Dec. 31, 2010 Non-Qualified Employee Purchase Plan 1998 [Member] Minimum [Member]	Dec. 31, 2011 Non-Qualified Employee Purchase Plan 1998 [Member] Maximum [Member]	Dec. 31, 2010 Non-Qualified Employee Purchase Plan 1998 [Member] Maximum [Member]	Dec. 31, 2011 Employee stock purchase plan [Member]	Dec. 31, 2010 Employee stock purchase plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance of awards (in shares)																																															5,000	8,450			4,400							1,100
Share-based Compensation Award Vesting Period													9 years 11 months																														3 years	5 years	3 years	5 years
Plan vesting period													9 years 11 months																														3 years	5 years	3 years	5 years
Expiration term																																								10 years
Assumptions used in computing the fair value [Abstract]
Expected volatility, minimum (in hundredths)																				70.00%	68.00%	68.00%																																									43.00%	45.00%
Expected volatility, maximum (in hundredths																				85.00%	78.00%	87.00%																																									51.00%	72.00%
Expected dividends (in hundredths)																				0.00%	0.00%	0.00%																																									0.00%	0.00%
Expected term (years)										5 years 4 months 24 days	5 years 3 months 18 days	5 years 3 months 18 days		8 years	8 years	10 years	7 years 4 months 24 days	7 years 4 months 24 days	7 years 3 months 18 days				5 years 3 months 18 days	5 years 3 months 18 days	5 years 3 months 18 days	10 years	10 years	10 years																																			6 months	6 months
Weighted average expected term (years)																				6 years 1 month 10 days	6 years 2 months 1 day	6 years 11 months 1 day
Risk-free rate, minimum (in hundredths)																				0.57%	0.77%	1.21%																																									0.06%	0.11%
Risk-free rate, maximum (in hundredths)																				1.71%	2.97%	3.09%																																									0.22%	0.18%
Options, Outstanding [Roll Forward]
Outstanding, Beginning balance (in shares)	5,597
Granted (in shares)	814																												113	145	75	38	113	33
Exercised (in shares)	(38)
Forfeited or expired (in shares)	(1,007)
Outstanding, Ending balance (in shares)	5,366	5,597
Exercisable (in shares)	3,970
Weighted Average Exercise Price [Roll Forward]
Outstanding, Beginning balance (in dollars per share)	$ 12.60
Granted (in dollars per share)	$ 9.54
Exercised (in dollars per share)	$ 5.28
Forfeited or expired (in dollars per share)	$ 12.16
Outstanding, Ending balance (in dollars per share)	$ 12.27	$ 12.60
Exercisable (in dollars per share)	$ 13.72
Weighted Average Remaining Contractual Term [Abstract]
Options Outstanding	5 years 7 months 10 days
Options Exercisable	4 years 9 months 7 days
Aggregate Intrinsic Value [Abstract]
Options Outstanding	$ 1,000
Options Exercisable	1,000
Weighted average grant-date fair value of options granted (in dollars per share)																																								$ 6.38	$ 5.51	$ 3.10
Total Intrinsic Value of options exercised																																								174,000	345,000	0
Estimated requisite service periods	3 years 6 months
Total compensation expense recognized	6,536,000	6,362,000	9,515,000	4,568,000	4,499,000	5,091,000	1,968,000	1,863,000	4,424,000																												2,000,000	400,000	1,100,000
Restricted Stock [Roll Forward]
Nonvested, Beginning balance (in shares)	98																																		98	341
Granted (in shares)	0
Vested (in shares)	(64)
Forfeited (in shares)	(6)
Nonvested, Ending balance (in shares)	28	98																																	28	341
Restricted Stock, Weighted Average Grant-Date Fair Value [Roll Forward]
Nonvested, Beginning balance (in dollars per share)	$ 7.40
Granted (in dollars per share)	$ 0
Vested (in dollars per share)	$ 8.50
Forfeited (in dollars per share)	$ 5.35
Nonvested, Ending balance (in dollars per share)	$ 5.35	$ 7.40
Percentage of quarterly compensation, grant to all employees (in hundredths)	25.00%
Discounted price as percentage of the fair market value (in hundredths)	85.00%
Employee stock purchase plan [Abstract]
Shares Purchased (in shares)																																																	428	802						162	208
Price Range (in dollars per share)																																																				$ 4.62	$ 3.50	$ 5.65	$ 4.56				$ 4.62	$ 3.75	$ 5.65	$ 4.56
Weighted Average Grant-date Fair value (in dollars per share)																																																	$ 0.88	$ 0.94						$ 0.84	$ 0.96
Total unrecognized compensation																				5,100,000															100,000
Weighted average periods																				1 year 9 months 18 days															6 months
Cash received from exercises under all share-based payment arrangements	300,000
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated Share-based Compensation Expense	$ 6,536,000	$ 6,362,000	$ 9,515,000	$ 4,568,000	$ 4,499,000	$ 5,091,000	$ 1,968,000	$ 1,863,000	$ 4,424,000																												$ 2,000,000	$ 400,000	$ 1,100,000