Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Deferred tax assets:
Net operating loss carryforwards	$ 359,000,000	$ 311,000,000
Deferred revenues	56,000,000	63,000,000
Capitalized research and development expenditures	35,000,000	34,000,000
Research and development tax credit carryforwards	37,000,000	34,000,000
Other	31,000,000	26,000,000
Valuation allowance	(518,000,000)	(468,000,000)
Information related to valuation allowance
Increase in valuation allowance	50,000,000	35,000,000	32,000,000
Gross unrecognized tax benefits
Gross unrecognized tax benefits at the beginning of the period	42,600,000	39,600,000	36,200,000
Gross decrease for tax positions for prior years			(100,000)
Gross increase in tax positions for current year	4,300,000	3,000,000	3,500,000
Gross unrecognized tax benefits at the end of the period	46,900,000	42,600,000	39,600,000
Federal
Operating Loss and Tax Credit Carryforward [Line Items]
Net operating loss carryfowards	1,068,200,000
Federal | Research and Development
Operating Loss and Tax Credit Carryforward [Line Items]
Tax credit carryforward amount	43,200,000
State
Operating Loss and Tax Credit Carryforward [Line Items]
Net operating loss carryfowards	425,000,000
State | Research
Operating Loss and Tax Credit Carryforward [Line Items]
Tax credit carryforward amount	$ 46,900,000