FINANCIAL INSTRUMENTS - Assets and Liabilities at Fair Value (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Assets:
Total assets			$ 3,617,788	$ 3,997,786
Liabilities:
Total liabilities				(19,231,331)
Quoted prices in active markets for identical assets Level 1
Assets:
Total assets	$ 0	$ 0
Liabilities:
Total liabilities		0
Significant other observable inputs Level 2
Assets:
Total assets	0	0
Liabilities:
Total liabilities		(19,231,331)
Unobservable inputs Level 3
Assets:
Total assets	3,617,788	3,997,786
Liabilities:
Total liabilities		0
Mortgage servicing rights
Assets:
Total assets			$ 3,617,788	3,997,786
Mortgage servicing rights | Quoted prices in active markets for identical assets Level 1
Assets:
Total assets	0	0
Mortgage servicing rights | Significant other observable inputs Level 2
Assets:
Total assets	0	0
Mortgage servicing rights | Unobservable inputs Level 3
Assets:
Total assets	$ 3,617,788	3,997,786
Multi-family securitized debt obligations
Liabilities:
Total liabilities				$ (19,231,331)
Multi-family securitized debt obligations | Quoted prices in active markets for identical assets Level 1
Liabilities:
Total liabilities		0
Multi-family securitized debt obligations | Significant other observable inputs Level 2
Liabilities:
Total liabilities		(19,231,331)
Multi-family securitized debt obligations | Unobservable inputs Level 3
Liabilities:
Total liabilities		$ 0