FAIR VALUE (Fair Value Measurements By Level 3 Valuation Technique) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Valuation technique weighting factor for NOI annual growth rate (as percentage)	10.00%
Valuation technique weighting factor for contract price (as percentage)	90.00%
Available-for-sale, Multifamily Tax-exempt , Performing Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 48,221,000
Available-for-sale, Multifamily Tax-exempt , Non-performing Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
NOI annual growth rate	0.50%
Contract price	$ 13,500,000
Available-for-sale, Multifamily Tax-exempt , Non-performing Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 12,882,000
Debt Securities, Available-for-sale, Measurement Input	8.2
Available-for-sale, Multifamily Tax-exempt , Non-performing Bonds [Member] | Measurement Input, Cap Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	7.0
Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 11,114,000	$ 8,721,000
Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input		7.3
Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Cap Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input		6.4
Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, NOI Annual Growth Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input		0.6
Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Contract Price [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input		16,100,000
Available-for-sale, Infrastructure Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 24,973,000	$ 25,400,000
Available-for-sale, Infrastructure Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	7.2	7.1
Total Return Swap [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 1,130,000
Minimum [Member] | Available-for-sale, Multifamily Tax-exempt , Performing Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	4.4
Minimum [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
NOI annual growth rate	0.60%
Minimum [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	7.4
Minimum [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Cap Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	6.2
Minimum [Member] | Total Return Swap [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Derivative Asset, Measurement Input	4.7
Maximum [Member] | Available-for-sale, Multifamily Tax-exempt , Performing Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	6.8
Maximum [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
NOI annual growth rate	0.70%
Maximum [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	7.6
Maximum [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Cap Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	6.5
Maximum [Member] | Total Return Swap [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Derivative Asset, Measurement Input	4.8
Weighted Average [Member] | Available-for-sale, Multifamily Tax-exempt , Performing Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	4.8
Weighted Average [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	7.5
Weighted Average [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, Cap Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	6.4
Weighted Average [Member] | Available-for-sale, Multifamily Tax-exempt, Subordinated Cash Flow Bonds [Member] | Measurement Input, NOI Annual Growth Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.7
Weighted Average [Member] | Total Return Swap [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Derivative Asset, Measurement Input	4.8