RELATED PARTY TRANSACTIONS (Details) - USD ($)		3 Months Ended			9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Investment Income		$ (63,976,000)		$ (32,945,000)	$ (36,445,000)		$ (23,326,000)
Debt instruments		1,737,000			1,737,000			$ 22,473,000
Listed equity securities		1,195,864,000			$ 1,195,864,000			844,001,000
Investment Advisory Agreement | Board of Directors Chairman
Related Party Transaction [Line Items]
Performance compensation full rate					20.00%
Performance compensation reduced rate					10.00%
Loss carry forward recoupment required					150.00%
Performance compensation expense		4,000,000		2,400,000	$ 4,000,000		2,400,000
Investment management fee rate - monthly					0.125%
Investment management fee rate - annual					1.50%
Management fees		4,400,000		$ 4,000,000	$ 13,100,000		$ 12,300,000
Equity Securities [Member] | Board of Directors Chairman
Related Party Transaction [Line Items]
Listed equity securities		34,300,000			34,300,000			34,800,000
Service Agreement [Member] | Board of Directors Chairman
Related Party Transaction [Line Items]
Investor relations monthly fee					5,000
Private Equity Funds [Member]
Related Party Transaction [Line Items]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months		7,214,000	[1]		7,214,000	[1]		$ 9,200,000
Unrecorded Unconditional Purchase Obligation, Due within Two Years	[1]	0			0
Unrecorded Unconditional Purchase Obligation, Due within Three Years	[1]	0			0
Unrecorded Unconditional Purchase Obligation, Due within Four Years	[1]	0			0
Unrecorded Unconditional Purchase Obligation, Due within Five Years	[1]	0			0
Unrecorded Unconditional Purchase Obligation, Due after Five Years	[1]	0			0
Unrecorded Unconditional Purchase Obligation	[1]	$ 7,214,000			$ 7,214,000

[1] Given the nature of these investments, the Company is unable to determine with any degree of accuracy when these commitments will be called. Therefore, for purposes of the above table, the Company has assumed that all commitments with no fixed payment schedules will be called during the year ending December 31, 2017