Revenues - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 715,440	$ 730,471	$ 726,044
Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	330,221	338,076
Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	385,219	392,395
United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	516,959	529,417	537,200
International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	198,481	201,054
Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	506,929	512,810
Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	208,511	217,661
A&D
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	314,824	351,876	325,700
A&D | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	136,449	160,402
A&D | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	178,375	191,474
A&D | United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	275,976	302,711
A&D | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	38,848	49,165
A&D | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	130,217	169,484
A&D | Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	184,607	182,392
USG
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	202,908	191,703	211,900
USG | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	153,163	144,192
USG | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	49,745	47,511
USG | United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	140,545	134,601
USG | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	62,363	57,102
USG | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	199,111	184,906
USG | Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	3,797	6,797
Test
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	197,708	186,892	$ 188,400
Test | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	40,609	33,482
Test | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	157,099	153,410
Test | United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	100,438	92,105
Test | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	97,270	94,787
Test | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	177,601	158,420
Test | Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 20,107	$ 28,472