MANDATORILY REDEEMABLE NONCONTROLLING INTEREST (ROLLFORWARD TABLE) (DETAILS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Mandatorily redeemable noncontrolling interest [Line Items]
Net income attributable to mandatorily redeemable noncontrolling interest	$ 10,812	$ 37,435	$ 65,885
Change in redemption value		(466)	(1,113)
Purchase of mandatorily redeemable noncontrolling interest	$ 0	(4,105)	0
Iknowtion
Mandatorily redeemable noncontrolling interest [Line Items]
ownership percentage	100.00%
Mandatorily redeemable noncontrolling interest, January 1		4,131
Working capital distributed to mandatorily redeemable noncontrolling interest		(492)
Change in redemption value		466
Purchase of mandatorily redeemable noncontrolling interest		$ (4,105)
Mandatorily redeemable noncontrolling interest, December 31			$ 4,131