Condensed Consolidated Statements of Comprehensive Earnings - Unaudited - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 7,209	$ 9,966	$ 18,757	$ 18,450
Other comprehensive income:
Changes in fair market value of derivatives, net of tax	67	(152)	874	608
Changes in unrealized pension cost, net of tax	1,249	942	2,356	1,758
Cumulative translation adjustment, net of tax	(375)	200	(132)	288
Other comprehensive income	941	990	3,098	2,654
Comprehensive earnings	$ 8,150	$ 10,956	$ 21,855	$ 21,104

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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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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