Condensed Consolidated Statements of Comprehensive Earnings - Unaudited - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net earnings	$ 11,943	$ 7,209	$ 23,362	$ 18,757
Other comprehensive income:
Changes in fair market value of derivatives, net of tax	(294)	67	(216)	874
Changes in unrealized pension cost, net of tax	1,026	1,249	2,048	2,356
Cumulative translation adjustment, net of tax	(87)	(375)	4	(132)
Other comprehensive income	645	941	1,836	3,098
Comprehensive income	$ 12,588	$ 8,150	$ 25,198	$ 21,855

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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