Annual report pursuant to Section 13 and 15(d)

Derivative Instruments and Hedging Activites - Effects on statements of income and consolidated statements of comprehesive income (Details)

v2.4.0.6
Derivative Instruments and Hedging Activites - Effects on statements of income and consolidated statements of comprehesive income (Details) (Not Designated as Hedging Instrument [Member], Interest Rate Swap, USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Not Designated as Hedging Instrument [Member] | Interest Rate Swap
      
Derivative Instruments, Gain (Loss) [Line Items]      
Amount of Gain (Loss) Recognized in Income on Derivative $ 98,026 $ 1,313,587 $ 1,346,041