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Retirement Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |  |  |
Retirement plan contribution by company | $ 2.6 | $ 1.9 | $ 2.1

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- Details
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Namespace Prefix: | us-gaap_
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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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