DEBT - Schedule (Details) - USD ($)	1 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Debt
Total Debt	$ 780,016,000	$ 780,016,000	$ 967,886,000
Mortgages Payable
Debt
Gross debt	416,300,000	416,300,000	532,437,000
Deferred loan costs	(1,582,000)	(1,582,000)	(2,366,000)
Premiums and discounts	0	0	722,000
Total Debt	414,718,000	414,718,000	530,793,000
Mortgage loan with a fixed interest of 4.14% per annum, due on July 1, 2026
Debt
Gross debt	$ 370,300,000	$ 370,300,000	392,000,000
Fixed interest rate	4.14%	4.14%
Amount of balance due on maturity	$ 370,300,000	$ 370,300,000
Mortgage loan with a fixed interest of 4.50% per annum, due on January 5, 2027
Debt
Gross debt	$ 46,000,000	$ 46,000,000	46,000,000
Fixed interest rate	4.50%	4.50%
Period of amortization schedule		10 years
Amount of balance due on maturity	$ 42,008,000	$ 42,008,000
Mortgage loan with a fixed interest of 5.39% per annum, due on March 1, 2021
Debt
Gross debt	0	0	$ 39,134,000
Fixed interest rate			5.39%
Amount of balance due on maturity			$ 35,695,000
Mortgage loan with a fixed interest of 5.18% per annum, due on June 5, 2021
Debt
Gross debt	0	0	$ 29,167,000
Fixed interest rate			5.18%
Amount of balance due on maturity			$ 26,232,000
Mortgage loan with a fixed interest of 6.65% per annum, due on July 15, 2018
Debt
Gross debt	0	0	$ 26,136,000
Fixed interest rate			6.65%
Period of amortization schedule			25 years
Amount of balance due on maturity			$ 21,136,000
Secured Borrowings - Government Guaranteed Loans
Debt
Gross debt	20,933,000	20,933,000	27,899,000
Premiums and discounts	1,490,000	1,490,000	2,077,000
Total Debt	22,423,000	22,423,000	29,976,000
Secured borrowing principal on SBA 7(a) loans sold for a premium and excess spread—variable rate, reset quarterly, based on prime rate with weighted average coupon rate of 5.19% and 4.13% at September 30, 2017 and December 31, 2016, respectively.
Debt
Gross debt	$ 17,015,000	$ 17,015,000	$ 23,122,000
Weighted average rate	5.19%	5.19%	4.13%
Secured borrowing principal on SBA 7(a) loans sold for excess spread—variable rate, reset quarterly, based on prime rate with weighted average coupon rate of 2.60% and 1.83% at September 30, 2017 and December 31, 2016, respectively.
Debt
Gross debt	$ 3,918,000	$ 3,918,000	$ 4,777,000
Weighted average rate	2.60%	2.60%	1.83%
Other Debt
Debt
Gross debt	$ 347,070,000	$ 347,070,000	$ 412,070,000
Total Debt	342,875,000	342,875,000	407,117,000
Unsecured term loan facility
Debt
Gross debt	320,000,000	320,000,000	385,000,000
Junior subordinated notes
Debt
Gross debt	27,070,000	27,070,000	27,070,000
Premiums and discounts	(1,957,000)	$ (1,957,000)	(2,015,000)
Junior subordinated notes | LIBOR
Debt
Interest rate margin		3.25%
Unsecured credit facilities
Debt
Gross debt	0	$ 0	0
Unsecured term loan and credit facilities
Debt
Deferred loan costs	(2,238,000)	$ (2,238,000)	$ (2,938,000)
Disposal Group, Held-for-sale, Not Discontinued Operations | Mortgage loan with a fixed interest of 4.14% per annum, due on July 1, 2026
Debt
Debt, gross	$ 21,700,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Mortgage loan with a fixed interest of 5.18% per annum, due on June 5, 2021
Debt
Fixed interest rate	5.18%	5.18%