Property And Equipment (Schedule Of Property And Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Property And Equipment [Abstract]
Purchased and internally developed software	$ 73,561	$ 62,731
Portable People Meter equipment	49,601	45,240
Computer equipment	21,776	21,231
Leasehold improvements	17,833	17,537
Machinery, furniture and fixtures	8,598	9,221
Property and equipment, Gross	171,369	155,960
Accumulated depreciation and amortization	(100,718)	(85,628)
Property and equipment, net	$ 70,651	$ 70,332

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, 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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