REVENUES - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 249,129	$ 229,136	$ 467,443	$ 434,637
Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	134,049	123,303	248,197	222,039
Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	115,080	105,833	219,246	212,598
United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	175,467	163,040	333,582	305,856
International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	73,662	66,096	133,861	128,781
Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	169,139	169,526	322,895	322,421
Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	79,990	59,610	144,548	112,216
A&D
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	114,701	98,982	209,434	181,965
A&D | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	53,463	47,255	92,928	80,859
A&D | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	61,238	51,727	116,506	101,106
A&D | United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	92,161	82,516	172,062	151,450
A&D | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	22,540	16,466	37,372	30,515
A&D | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	49,382	48,228	86,591	84,968
A&D | Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	65,319	50,754	122,843	96,997
USG
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	87,309	79,161	170,293	150,206
USG | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	70,285	64,080	136,989	120,111
USG | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	17,024	15,081	33,304	30,095
USG | United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	55,763	53,020	111,725	99,399
USG | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	31,546	26,141	58,568	50,807
USG | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	85,220	78,110	166,689	148,273
USG | Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	2,089	1,051	3,604	1,933
Test
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	47,119	50,993	87,716	102,466
Test | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	10,301	11,968	18,280	21,069
Test | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	36,818	39,025	69,436	81,397
Test | United States
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	27,543	27,504	49,795	55,007
Test | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	19,576	23,489	37,921	47,459
Test | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	34,537	43,188	69,615	89,180
Test | Government
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 12,582	$ 7,805	$ 18,101	$ 13,286