CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (unaudited) [Abstract]
Net earnings (loss) available to common stockholders	$ 3,120	$ 22,776	$ 3,866	$ (77,921)
Other comprehensive income (loss):
Currency translation adjustment, net of taxes of $153 in the three months ended June 30, 2017, $0 in the three months ended June 30, 2016, $184 in the six months ended June 30, 2017 and $0 in the six months ended June 30, 2016	5,661	(4,071)	7,572	(3,043)
Unrealized gains (losses) on marketable securities arising during the period, net of taxes of $7 in the three months ended June 30, 2017, $33 in the three months ended June 30, 2016, $(170) in the six months ended June 30, 2017 and $60 in the six months ended June 30, 2016	12	54	(267)	98
Change in unfunded SERP liability, net of taxes of $32 in the three months ended June 30, 2017, $32 in the three months ended June 30, 2016, $65 in the six months ended June 30, 2017 and $104 in the six months ended June, 2016	61	66	122	500
Other comprehensive income (loss)	5,734	(3,951)	7,427	(2,445)
Comprehensive income (loss)	$ 8,854	$ 18,825	$ 11,293	$ (80,366)