Property and Equipment (Details) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Property and Equipment
Property and equipment, gross	$ 57,764,000	$ 53,861,000
Less accumulated depreciation and amortization	(47,392,000)	(43,646,000)
Property and equipment, net	10,372,000	10,215,000
Depreciation expense	3,800,000	3,900,000	4,300,000
Computer equipment
Property and Equipment
Property and equipment, gross	3,158,000	2,473,000
Software
Property and Equipment
Property and equipment, gross	4,628,000	4,592,000
Furniture and fixtures
Property and Equipment
Property and equipment, gross	3,821,000	3,689,000
Laboratory equipment
Property and Equipment
Property and equipment, gross	28,894,000	27,006,000
Leasehold improvements
Property and Equipment
Property and equipment, gross	$ 17,263,000	$ 16,101,000

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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- Definition

Gross amount, at the balance sheet date, of long-lived physical assets used in the normal conduct of business and not intended for resale. This can include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

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- Definition

Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

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