Acquisitions and Divestitures (Summary of Results of Discontinued Operations (Parenthetical)) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, tax	$ 2,229

Amount of tax expense or benefit on gain (loss), not previously recognized, resulting from the sale of a business component.

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