Condensed Consolidated Statements of Comprehensive Earnings - Unaudited - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net earnings	$ 9,619	$ 3,720	$ 28,069	$ 26,070
Other comprehensive income (loss):
Changes in fair market value of derivatives, net of tax	(45)	(263)	563	(36)
Changes in unrealized pension cost, net of tax	936	898	2,694	2,753
Cumulative translation adjustment, net of tax	164	(164)	452	(890)
Other comprehensive income	1,055	471	3,709	1,827
Comprehensive earnings	$ 10,674	$ 4,191	$ 31,778	$ 27,897

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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