FAIR VALUE OF FINANCIAL INSTRUMENTS (Details 4)	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) $ / barrel	Dec. 31, 2016 USD ($) $ / shares $ / barrel	Dec. 31, 2015 USD ($)
Crude Oil
Valuation techniques used for assets, measured at fair value
Percentage of share in total revenue	24.00%	23.00%
Natural Gas
Valuation techniques used for assets, measured at fair value
Percentage of share in total revenue	76.00%	77.00%
Natural Resources
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 87,200,000		$ 107,300,000
Minimum
Valuation techniques used for assets, measured at fair value
Weight ascribed to each valuation technique	0.00%	0.00%
Maximum
Valuation techniques used for assets, measured at fair value
Weight ascribed to each valuation technique	100.00%	100.00%
Significant Unobservable Inputs (Level 3) | Corporate Debt Securities
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 227,198,000	$ 175,206,000
Significant Unobservable Inputs (Level 3) | Residential Mortgage- Backed Securities
Valuation techniques used for assets, measured at fair value
Assets, fair value	39,286,000	40,663,000
Significant Unobservable Inputs (Level 3) | Corporate Loans
Valuation techniques used for assets, measured at fair value
Assets, fair value	125,088,000	129,194,000
Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 131,125,000	$ 132,305,000
Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Minimum
Valuation techniques used for assets, measured at fair value
Illiquidity discount	5.00%	5.00%
Significant Unobservable Inputs (Level 3) | Corporate Debt Securities and Equity Investments
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 462,100,000	$ 408,100,000
Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships
Valuation techniques used for assets, measured at fair value
Assets, fair value	841,733,000	793,996,000
Significant Unobservable Inputs (Level 3) | Foreign Exchange Options, Net
Valuation techniques used for assets, measured at fair value
Assets, fair value	816,000	992,000
Significant Unobservable Inputs (Level 3) | Options
Valuation techniques used for assets, measured at fair value
Assets, fair value	1,464,000	1,001,000
Significant Unobservable Inputs (Level 3) | Warrants
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 1,700,000	$ 1,500,000
Yield analysis | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Weighted Average
Valuation techniques used for assets, measured at fair value
Yield	22.00%	14.00%
Net leverage	30	9
EBITDA multiple	37	6
Discount margin	11.51%	11.05%
Yield analysis | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Minimum
Valuation techniques used for assets, measured at fair value
Yield	5.00%	5.00%
Net leverage	15	7
EBITDA multiple	0	0
Discount margin	11.00%	11.00%
Yield analysis | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Maximum
Valuation techniques used for assets, measured at fair value
Yield	23.00%	15.00%
Net leverage	31	16
EBITDA multiple	39	9
Discount margin	16.00%	11.50%
Yield analysis | Significant Unobservable Inputs (Level 3) | Corporate Loans | Weighted Average
Valuation techniques used for assets, measured at fair value
Yield	12.00%	13.00%
Net leverage	15	11
EBITDA multiple	10	6
Weight ascribed to market comparables	1.00%
Weight ascribed to discounted cash flows	1.00%
Weight ascribed to yield analysis	98.00%
Yield analysis | Significant Unobservable Inputs (Level 3) | Corporate Loans | Minimum
Valuation techniques used for assets, measured at fair value
Yield	10.00%	11.00%
Net leverage	5	5
EBITDA multiple	7	0
Weight ascribed to market comparables	0.00%
Weight ascribed to discounted cash flows	0.00%
Weight ascribed to yield analysis	0.00%
Yield analysis | Significant Unobservable Inputs (Level 3) | Corporate Loans | Maximum
Valuation techniques used for assets, measured at fair value
Yield	15.00%	16.00%
Net leverage	91	82
EBITDA multiple	23	19
Weight ascribed to market comparables	50.00%
Weight ascribed to discounted cash flows	50.00%
Weight ascribed to yield analysis	100.00%
Yield analysis | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 26,900,000	$ 24,400,000
Yield analysis | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Weighted Average
Valuation techniques used for assets, measured at fair value
Yield	27.00%	19.00%
Net leverage	2	2
EBITDA multiple	7	7
Yield analysis | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Minimum
Valuation techniques used for assets, measured at fair value
Yield	27.00%	19.00%
Net leverage	2	2
EBITDA multiple	7	7
Yield analysis | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Maximum
Valuation techniques used for assets, measured at fair value
Yield	27.00%	19.00%
Net leverage	2	2
EBITDA multiple	7	7
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Residential Mortgage- Backed Securities | Weighted Average
Valuation techniques used for assets, measured at fair value
Probability of default	2.00%	2.00%
Loss severity	43.00%	43.00%
Constant prepayment rate	16.00%	18.00%
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Residential Mortgage- Backed Securities | Minimum
Valuation techniques used for assets, measured at fair value
Probability of default	0.00%	0.00%
Loss severity	35.00%	35.00%
Constant prepayment rate	12.00%	12.00%
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Residential Mortgage- Backed Securities | Maximum
Valuation techniques used for assets, measured at fair value
Probability of default	3.00%	3.00%
Loss severity	50.00%	50.00%
Constant prepayment rate	20.00%	23.00%
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Corporate Loans | Weighted Average
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	15.00%
LTM EBITDA exit multiple	6
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Corporate Loans | Minimum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	15.00%
LTM EBITDA exit multiple	6
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Corporate Loans | Maximum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	15.00%
LTM EBITDA exit multiple	6
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 19,900,000	$ 20,000,000
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Weighted Average
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	9.00%	9.00%
LTM EBITDA exit multiple	8	8
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Minimum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	7.00%	7.00%
LTM EBITDA exit multiple	5	7
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Maximum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	15.00%	14.00%
LTM EBITDA exit multiple	10	10
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 47,100,000	$ 43,500,000
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Weighted Average
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	10.00%	10.00%
Average price per BOE (in dollars per barrel) | $ / barrel	19.92	20.26
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Minimum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	6.00%	6.00%
Average price per BOE (in dollars per barrel) | $ / barrel	18.35	18.81
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Maximum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	20.00%	20.00%
Average price per BOE (in dollars per barrel) | $ / barrel	22.35	22.38
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Options | Weighted Average
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	15.00%	15.00%
LTM EBITDA exit multiple	6	5
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Options | Minimum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	15.00%	15.00%
LTM EBITDA exit multiple	6	5
Discounted cash flows | Significant Unobservable Inputs (Level 3) | Options | Maximum
Valuation techniques used for assets, measured at fair value
Weighted average cost of capital	15.00%	15.00%
LTM EBITDA exit multiple	6	5
Option pricing model | Significant Unobservable Inputs (Level 3) | Weighted Average | Foreign Exchange Options, Net
Valuation techniques used for assets, measured at fair value
Forward and spot rates	$ 13,309	$ 10,301
Option pricing model | Significant Unobservable Inputs (Level 3) | Minimum | Foreign Exchange Options, Net
Valuation techniques used for assets, measured at fair value
Forward and spot rates	13,309	6
Option pricing model | Significant Unobservable Inputs (Level 3) | Maximum | Foreign Exchange Options, Net
Valuation techniques used for assets, measured at fair value
Forward and spot rates	$ 13,309	$ 13,550
Market comparables | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Weighted Average
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple		12
Market comparables | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Minimum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple		12
Market comparables | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Maximum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple		12
Market comparables | Significant Unobservable Inputs (Level 3) | Corporate Loans | Weighted Average
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	9
Forward EBITDA multiple	8
Market comparables | Significant Unobservable Inputs (Level 3) | Corporate Loans | Minimum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	9
Forward EBITDA multiple	8
Market comparables | Significant Unobservable Inputs (Level 3) | Corporate Loans | Maximum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	9
Forward EBITDA multiple	8
Market comparables | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 15,200,000	$ 14,500,000
Market comparables | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Weighted Average
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	11	11
Forward EBITDA multiple	10	9
Market comparables | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Minimum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	0	0
Forward EBITDA multiple	0	0
Market comparables | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Maximum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	16	14
Forward EBITDA multiple	14	13
Market comparables | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships
Valuation techniques used for assets, measured at fair value
Assets, fair value	$ 8,800,000	$ 9,800,000
Market comparables | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Weighted Average
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	1	4
Capitalization rate	7.00%	7.00%
Forward EBITDA multiple	1	9
Market comparables | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Minimum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	1	1
Capitalization rate	4.00%	3.00%
Forward EBITDA multiple	1	9
Market comparables | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Maximum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	1	9
Capitalization rate	12.00%	12.00%
Forward EBITDA multiple	1	9
Market comparables | Significant Unobservable Inputs (Level 3) | Options | Weighted Average
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	9	9
Forward EBITDA multiple	8	7
Market comparables | Significant Unobservable Inputs (Level 3) | Options | Minimum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	9	9
Forward EBITDA multiple	8	7
Market comparables | Significant Unobservable Inputs (Level 3) | Options | Maximum
Valuation techniques used for assets, measured at fair value
LTM EBITDA multiple	9	9
Forward EBITDA multiple	8	7
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Weighted Average
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	47.00%	47.00%
Weight ascribed to discounted cash flows	53.00%	53.00%
Illiquidity discount	11.00%	8.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Minimum
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	0.00%	0.00%
Weight ascribed to discounted cash flows	0.00%	0.00%
Illiquidity discount	0.00%	5.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Equity Investments, at Estimated Fair Value | Maximum
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	100.00%	100.00%
Weight ascribed to discounted cash flows	100.00%	100.00%
Illiquidity discount	15.00%	15.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Weighted Average
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	25.00%	27.00%
Weight ascribed to discounted cash flows	43.00%	45.00%
Weight ascribed to yield analysis	32.00%	28.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Minimum
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	0.00%	0.00%
Weight ascribed to discounted cash flows	0.00%	0.00%
Weight ascribed to yield analysis	0.00%	0.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Interests in Joint Ventures and Partnerships | Maximum
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	100.00%	100.00%
Weight ascribed to discounted cash flows	100.00%	100.00%
Weight ascribed to yield analysis	100.00%	100.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Options
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	50.00%	50.00%
Weight ascribed to discounted cash flows	50.00%	50.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Options | Weighted Average
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	50.00%	50.00%
Weight ascribed to discounted cash flows	50.00%	50.00%
Illiquidity discount	10.00%	10.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Options | Minimum
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	50.00%	50.00%
Weight ascribed to discounted cash flows	50.00%	50.00%
Illiquidity discount	10.00%	10.00%
Inputs to both market comparables and discounted cash flow | Significant Unobservable Inputs (Level 3) | Options | Maximum
Valuation techniques used for assets, measured at fair value
Weight ascribed to market comparables	50.00%	50.00%
Weight ascribed to discounted cash flows	50.00%	50.00%
Illiquidity discount	10.00%	10.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Weighted Average
Valuation techniques used for assets, measured at fair value
Risk-Free Rate		1.00%
Volatility		85.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Minimum
Valuation techniques used for assets, measured at fair value
Risk-Free Rate		1.00%
Volatility		85.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Maximum
Valuation techniques used for assets, measured at fair value
Risk-Free Rate		1.00%
Volatility		85.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Corporate Loans | Weighted Average
Valuation techniques used for assets, measured at fair value
Risk-Free Rate	3.00%
Volatility	28.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Corporate Loans | Minimum
Valuation techniques used for assets, measured at fair value
Risk-Free Rate	3.00%
Volatility	28.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Corporate Loans | Maximum
Valuation techniques used for assets, measured at fair value
Risk-Free Rate	3.00%
Volatility	28.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Options | Weighted Average
Valuation techniques used for assets, measured at fair value
Risk-Free Rate	3.00%
Volatility	28.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Options | Minimum
Valuation techniques used for assets, measured at fair value
Risk-Free Rate	3.00%
Volatility	28.00%
Black Scholes Options Pricing Model | Significant Unobservable Inputs (Level 3) | Options | Maximum
Valuation techniques used for assets, measured at fair value
Risk-Free Rate	3.00%
Volatility	28.00%
Offered Quotes | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Weighted Average
Valuation techniques used for assets, measured at fair value
Offered quotes (in dollars per share) | $ / shares		$ 102
Offered Quotes | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Minimum
Valuation techniques used for assets, measured at fair value
Offered quotes (in dollars per share) | $ / shares		101
Offered Quotes | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities | Maximum
Valuation techniques used for assets, measured at fair value
Offered quotes (in dollars per share) | $ / shares		$ 103