Loans and Investments, Impaired Loans (Details)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) loan	Dec. 31, 2014 USD ($) loan
Changes in allowance for loan losses
Allowance at beginning of period	$ 86,761,575	$ 115,487,320	$ 122,277,411
Provision for loan losses	59,005	6,509,149	9,026,712
Charge-offs	(2,959,005)	(32,000,000)	(6,501,079)
Charge-off on loan reclassified to real estate owned, net		(2,500,000)
Recoveries of reserves	(150,000)	(734,894)	(9,315,724)
Allowance at end of period	83,711,575	$ 86,761,575	$ 115,487,320
Number of impaired loans | loan		5	4
Carrying value of impaired loan		$ 125,300,000	$ 151,900,000
Net recoveries of previously recorded loan loss reserves		2,000,000	9,300,000
Provision for loan losses	(134,101)	4,466,886	(308,511)
Loans with previous reserves		4,000,000	3,800,000
Loans without previous reserves		2,500,000	$ 5,200,000
Junior participating loans
Changes in allowance for loan losses
Charge-offs		(32,000,000)
Transfer of land held as collateral
Changes in allowance for loan losses
Charge-offs		$ (2,500,000)
Bridge loans
Changes in allowance for loan losses
Charge-offs	$ (3,000,000)