Condensed Consolidated Statements of Comprehensive Earnings - Unaudited - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net earnings	$ 4,857	$ 11,943	$ 8,665	$ 23,362
Other comprehensive (loss) earnings:
Changes in fair market value of derivatives, net of tax	644	(294)	(3,770)	(216)
Changes in unrealized pension cost, net of tax	1,209	1,026	2,494	2,048
Cumulative translation adjustment, net of tax	(14)	(87)	(153)	4
Other comprehensive (loss) earnings	1,839	645	(1,429)	1,836
Comprehensive earnings	$ 6,696	$ 12,588	$ 7,236	$ 25,198