CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE EARNINGS - UNAUDITED - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net earnings	$ 11,990	$ 3,808
Other comprehensive earnings (loss):
Changes in fair market value of derivatives, net of tax	124	(4,414)
Changes in unrealized pension cost, net of tax	1,422	1,285
Cumulative translation adjustment, net of tax	12	(139)
Other comprehensive earnings (loss)	1,558	(3,268)
Comprehensive earnings	$ 13,548	$ 540