Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax		$ 100		$ 150	$ 100
Net earnings		19,896	$ 32,969	42,688	67,945
Currency translation		(38)	171	683	(814)
Postretirement plans (1)	[1]	119	118	239	232
Comprehensive income		$ 19,977	33,258	$ 43,610	$ 67,363
Maximum [Member]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax			$ 100

[1] Net of tax effect of $0.1 million and less than $0.1 million for the three months ended June 30, 2016 and 2015, respectively, and $0.2 million and $0.1 million for the six months ended June 30, 2016 and 2015.