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Interim Financial Statements Interim Financial Statements - Additional Information (Details)
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Sep. 30, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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| Organization, Consolidation and Presentation of Financial Statements [Abstract] | |||
| Common stock, shares authorized | 1,000,000,000 | 500,000,000 | 500,000,000 |