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 of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Property and equipment
Property and equipment, gross	$ 7,913		$ 7,913		$ 6,499
Less accumulated depreciation and amortization	(5,433)		(5,433)		(5,078)
Property and equipment, net	2,480		2,480		1,421
Depreciation expense	143	154	355	478
Computer equipment
Property and equipment
Property and equipment, gross	798		798		615
Software
Property and equipment
Property and equipment, gross	209		209		209
Lab equipment and furniture
Property and equipment
Property and equipment, gross	4,613		4,613		3,896
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 2,293		$ 2,293		$ 1,779