EARNINGS (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator [Abstract]
Net earnings (loss)	$ 5,024	$ 9,710	$ 8,890	$ (68,211)
Undistributed earnings (loss)	4,202	8,896	6,419	(70,647)
Class A [Member]
Numerator [Abstract]
Net earnings (loss)	860	1,688	1,507	(12,008)
Less dividends declared	131	131	392	392
Undistributed earnings (loss)	$ 729	$ 1,557	$ 1,115	$ (12,400)
Weighted-average shares outstanding [Abstract]
Basic and diluted (in shares)	2,175	2,175	2,175	2,175
Net earnings (loss) per share [Abstract]
Basic and diluted (in dollars per share)	$ 0.40	$ 0.78	$ 0.69	$ (5.52)
Class B [Member]
Numerator [Abstract]
Net earnings (loss)	$ 4,164	$ 8,022	$ 7,383	$ (56,203)
Less dividends declared	691	683	2,079	2,044
Undistributed earnings (loss)	$ 3,473	$ 7,339	$ 5,304	$ (58,247)
Weighted-average shares outstanding [Abstract]
Basic and diluted (in shares)	9,864	9,760	9,856	9,730
Net earnings (loss) per share [Abstract]
Basic and diluted (in dollars per share)	$ 0.42	$ 0.82	$ 0.75	$ (5.78)