REVENUES - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 204,928	$ 165,894	$ 381,938	$ 328,568
Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	101,706	73,938	193,920	152,047
Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	103,222	91,956	188,018	176,521
United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	145,150	122,697	267,559	240,545
International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	59,778	43,197	114,379	88,023
Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	148,844	111,077	280,651	229,530
Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	56,084	54,817	101,287	99,038
A&D
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	84,821	82,528	155,065	149,144
A&D | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	35,666	37,127	64,223	64,000
A&D | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	49,155	45,401	90,842	85,144
A&D | United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	72,621	72,287	133,313	129,824
A&D | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	12,200	10,241	21,752	19,320
A&D | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	33,562	33,223	61,489	61,089
A&D | Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	51,259	49,305	93,576	88,055
USG
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	64,191	39,555	127,676	94,095
USG | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	51,202	27,563	102,037	69,931
USG | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	12,989	11,992	25,639	24,164
USG | United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	41,458	27,445	80,199	64,490
USG | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	22,733	12,110	47,477	29,605
USG | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	63,379	38,549	126,221	92,414
USG | Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	812	1,006	1,455	1,681
Test
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	55,916	43,811	99,197	85,329
Test | Point in time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	14,838	9,248	27,660	18,116
Test | Over time
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	41,078	34,563	71,537	67,213
Test | United States [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	31,071	22,965	54,047	46,231
Test | International
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	24,845	20,846	45,150	39,098
Test | Commercial
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	51,903	39,305	92,941	76,027
Test | Government [Member]
Disaggregation of revenues
Revenue from contract with customer excluding assessed tax	$ 4,013	$ 4,506	$ 6,256	$ 9,302