Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with interest rate reset through auction process, sold at par value.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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AVAILABLE-FOR-SALE SECURITIES - Realized Gain (Loss) from Sale of AFS Securities (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Available for sale securities			$ 0	$ 0
AFS Securities
Debt Securities, Available-for-sale [Line Items]
AFS securities sold, at cost	$ 1,113,596,615	$ 1,260,655,159
Proceeds from AFS securities sold	1,083,104,038	1,227,314,575
Net realized gain (loss) on sale of AFS securities	$ (30,492,577)	$ (33,340,584)