Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity Share Repurchase Program (Details)

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Stockholders' Equity Share Repurchase Program (Details)
12 Months Ended
Dec. 31, 2012
Mar. 31, 2013
Dec. 31, 2011
Class of Stock [Line Items]      
Stock Repurchase Program, Number of Shares Authorized to be Repurchased   25,000,000 10,000,000
Stock Repurchase Program, Number of Additional Shares Authorized to be Repurchased 15,000,000