REVENUES - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 248,749	$ 219,066	$ 683,386	$ 601,004
Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	134,120	104,721	356,160	298,645
Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	114,629	114,345	327,226	302,359
United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	173,288	156,020	479,144	423,578
International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	75,461	63,046	204,242	177,426
Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	188,152	158,977	510,573	439,629
Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	60,597	60,089	172,813	161,375
Aerospace & Defense
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	103,469	92,606	285,434	247,671
Aerospace & Defense | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	48,496	35,238	129,355	99,464
Aerospace & Defense | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	54,973	57,368	156,079	148,207
Aerospace & Defense | United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	86,031	79,536	237,481	212,849
Aerospace & Defense | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	17,438	13,070	47,953	34,822
Aerospace & Defense | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	51,303	38,918	136,271	100,407
Aerospace & Defense | Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	52,166	53,688	149,163	147,264
USG
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	89,966	67,201	240,172	194,877
USG | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	74,128	53,656	194,240	155,693
USG | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	15,838	13,545	45,932	39,184
USG | United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	55,011	41,822	154,410	122,021
USG | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	34,955	25,379	85,762	72,856
USG | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	88,442	65,610	236,715	191,832
USG | Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	1,524	1,591	3,457	3,045
Test
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	55,314	59,259	157,780	158,456
Test | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	11,496	15,827	32,565	43,488
Test | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	43,818	43,432	125,215	114,968
Test | United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	32,246	34,662	87,253	88,708
Test | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	23,068	24,597	70,527	69,748
Test | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	48,407	54,449	137,587	147,390
Test | Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 6,907	$ 4,810	$ 20,193	$ 11,066