Condensed Consolidated Statements of Comprehensive Earnings - Unaudited - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net earnings	$ 9,966	$ 14,487	$ 18,450	$ 22,350
Other comprehensive income (loss):
Changes in fair market value of derivatives, net of tax	(152)	(67)	608	227
Changes in unrealized pension cost, net of tax	942	947	1,758	1,855
Cumulative translation adjustment, net of tax	200	(317)	288	(726)
Other comprehensive income	990	563	2,654	1,356
Comprehensive earnings	$ 10,956	$ 15,050	$ 21,104	$ 23,706

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 of other comprehensive income (loss) attributable to parent entity.

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