CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) [Abstract]
Net earnings available to common stockholders	$ 11,352	$ 5,024	$ 16,684	$ 8,890
Other comprehensive income (loss):
Currency translation adjustment, net of taxes of ($1) in the three months ended September 30, 2018, $101 in the three months ended September 30, 2017, $11 in the nine months ended September 30, 2018 and $285 in the nine months ended September 30, 2017	(1,032)	3,476	(4,463)	11,047
Unrealized (losses) on marketable securities arising during the period, net of taxes of $3 in the three months ended September 30, 2018, ($21) in the three months ended September 30, 2017, ($17) in the nine months ended September 30, 2018 and ($191) in the nine months ended September 30, 2017	(170)	(33)	(201)	(300)
Change in unfunded SERP liability, net of taxes of $25 in the three months ended September 30, 2018, $32 in the three months ended September 30, 2017, $76 in the nine months ended September 30, 2018 and $97 in the nine months ended September 30, 2017	85	61	256	184
Other comprehensive income (loss)	(1,117)	3,504	(4,408)	10,931
Comprehensive income	$ 10,235	$ 8,528	$ 12,276	$ 19,821