Property And Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,157	$ 3,211	$ 2,747
Accumulated depreciation and amortization	(2,901)	(2,784)	(2,300)
Property and equipment, net	256	427	447
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,446	1,508	1,259
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	425	421	401
Leasehold improvements, furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,286	$ 1,282	$ 1,087

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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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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