Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred tax assets:
Net operating loss carryforwards	$ 411,000,000	$ 359,000,000
Deferred revenues	4,000,000	56,000,000
Capitalized research and development expenditures	35,000,000	35,000,000
Research and development tax credit carryforwards	38,000,000	37,000,000
Other	33,000,000	31,000,000
Valuation allowance	(521,000,000)	(518,000,000)
Information related to valuation allowance
Increase in valuation allowance	3,000,000	50,000,000	35,000,000
The differences between the U.S. federal statutory income tax rate to the Company's effective tax rate
U.S. federal statutory income tax rate (as a percent)	34.00%	34.00%	34.00%
State income taxes, net of federal benefit (as a percent)			5.83%
Federal and state research credits	(4.21%)	1.67%	2.91%
Non-deductible executive compensation	(13.24%)
Stock-based compensation (as a percent)	(1.36%)	(0.32%)	2.29%
Expiration of net operating loss (as a percent)	(1.81%)	(0.42%)
Other (as a percent)	(2.09%)	0.75%	(0.05%)
Change in valuation allowance	(11.29%)	(35.68%)	(44.98%)
Effective tax rate (as a percent)	0.00%	0.00%	0.00%
Gross unrecognized tax benefits
Gross unrecognized tax benefits at the beginning of the period	46,900,000	42,600,000	39,600,000
Gross increase in tax positions for current year	5,600,000	4,300,000	3,000,000
Gross unrecognized tax benefits at the end of the period	52,500,000	46,900,000	42,600,000
Federal
Operating Loss and Tax Credit Carryforward
Net operating loss carryfowards	1,221,400,000
Federal | Research and Development
Operating Loss and Tax Credit Carryforward
Tax credit carryforward amount	43,200,000
State
Operating Loss and Tax Credit Carryforward
Net operating loss carryfowards	563,400,000
State | Research
Operating Loss and Tax Credit Carryforward
Tax credit carryforward amount	$ 52,200,000