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Employee Benefit Plan (Details) (USD $) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Compensation and Retirement Disclosure [Abstract] |  |  |
Company's contributions under 401(k) retirement savings plan | $ 2,490,000 | $ 2,253,000 | $ 1,970,000

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- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920 + Details
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