Condensed Consolidated Statements of Comprehensive Earnings - Unaudited - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net earnings	$ 2,722	$ 10,211	$ 26,084	$ 28,968
Other comprehensive income:
Changes in fair market value of derivatives, net of tax	(740)	624	(956)	1,498
Changes in unrealized pension cost, net of tax	1,017	1,157	3,065	3,513
Cumulative translation adjustment, net of tax	(92)	1	(88)	(131)
Other comprehensive income	185	1,782	2,021	4,880
Comprehensive income	$ 2,907	$ 11,993	$ 28,105	$ 33,848

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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