Operating Segments and Related Information (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 434,898	$ 464,712	$ 1,327,223	$ 1,305,650
Intersegment revenue	0	0	0	0
Earnings from operations	88,552	87,086	232,710	212,802
Government and Defense
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	171,955	169,734	492,313	453,630
Intersegment revenue	(2,327)	(3,896)	(8,428)	(7,163)
Earnings from operations	53,878	52,605	145,608	124,078
Industrial
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	177,151	170,942	536,231	490,463
Intersegment revenue	(3,455)	(4,786)	(15,950)	(9,728)
Earnings from operations	56,046	54,391	159,597	144,256
Commercial
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	85,792	124,036	298,679	361,557
Intersegment revenue	(5,845)	(4,265)	(13,926)	(8,065)
Earnings from operations	10,441	14,314	42,280	39,777
Eliminations
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Intersegment revenue	(11,627)	(12,947)	(38,304)	(24,956)
Total Segments [Member]
Business Unit Reporting, Revenue Reconciling Item [Line Items]
Revenue	434,898	464,712	1,327,223	1,305,650
Earnings from operations	$ 120,365	$ 121,310	$ 347,485	$ 308,111