Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Business Segment (Details)

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Summary of Significant Accounting Policies - Business Segment (Details) (USD $)
12 Months Ended
Dec. 31, 2012
segment
Dec. 31, 2011
Dec. 31, 2010
Accounting Policies [Abstract]      
Number of reportable segments 4    
Unallocated corporate expenses $ 44,399,958 $ 39,477,839 $ 30,721,689
Income before taxes and unallocated corporate expenses $ 18,088,251 $ 9,712,686 $ 8,662,872