FINANCIAL INSTRUMENTS Level 3 reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 6,763	$ 8,957
Purchases	1,750	0
Sales	0	(2,539)
Total realized and unrealized gains (losses) and amortization included in earnings, net		345
Transfers into Level 3	0	0
Transfers out of Level 3	(1,768)	0
Ending balance	6,988	6,763
Debt instruments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	654	505
Purchases	0	0
Sales	0	0
Total realized and unrealized gains (losses) and amortization included in earnings, net	226	149
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	880	654
Private and unlisted equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	6,109	8,452
Purchases	1,750	0
Sales	0	(2,539)
Total realized and unrealized gains (losses) and amortization included in earnings, net	17	196
Transfers into Level 3	0	0
Transfers out of Level 3	(1,768)	0
Ending balance	6,108	6,109
Financial contracts payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total realized and unrealized gains (losses) Included in earnings, Liabilities	243
Net investment income (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total realized and unrealized gains (losses) and amortization included in earnings, net	0	(1,400)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 200	$ 300