FAIR VALUE (Fair Value Measurements By Level 3 Valuation Technique) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Multifamily tax-exempt bonds, Performing
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 29,982	$ 48,221
Multifamily tax-exempt bonds, Non-performing
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 15,187	$ 12,882
Market yield	7.60%	8.20%
Capitalization rate	6.20%	7.00%
NOI annual growth rate	0.30%	0.50%
Contract price	$ 13,500	$ 13,500
Multifamily tax-exempt bonds, Subordinated cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	10,361	11,114
Infrastructure bonds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 25,572	24,973
Market yield	7.00%
Total return swaps
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 776	$ 1,130
Market yield	4.80%
Minimum | Multifamily tax-exempt bonds, Performing
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield	4.40%	4.40%
Minimum | Multifamily tax-exempt bonds, Subordinated cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield	7.50%	7.40%
Capitalization rate	6.30%	6.20%
NOI annual growth rate	0.50%	0.60%
Minimum | Infrastructure bonds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield		7.20%
Minimum | Total return swaps
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield		4.70%
Maximum | Multifamily tax-exempt bonds, Performing
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield	4.50%	6.80%
Maximum | Multifamily tax-exempt bonds, Subordinated cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield	7.80%	7.60%
Capitalization rate	6.60%	6.50%
NOI annual growth rate	0.80%	0.70%
Maximum | Total return swaps
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield		4.80%
Weighted Average | Multifamily tax-exempt bonds, Performing
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield	4.50%	4.80%
Weighted Average | Multifamily tax-exempt bonds, Subordinated cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield	7.60%	7.50%
Capitalization rate	6.50%	6.40%
NOI annual growth rate	0.70%	0.70%
Weighted Average | Total return swaps
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Market yield		4.80%