Operating Segments and Related Information (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 439,618	$ 406,814
Intersegment revenue	0	0
Earnings from operations	55,492	59,086
Government and Defense
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	159,331	138,180
Intersegment revenue	(1,528)	(3,267)
Earnings from operations	46,182	33,319
Industrial
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	170,658	154,785
Intersegment revenue	(6,332)	(4,941)
Earnings from operations	45,455	42,818
Commercial
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	109,629	113,849
Intersegment revenue	(4,481)	(3,800)
Earnings from operations	14,472	9,988
Eliminations
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Intersegment revenue	(12,341)	(12,008)
Total Segments [Member]
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	439,618	406,814
Earnings from operations	$ 106,109	$ 86,125