REVENUES - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of revenues
Total revenues	$ 199,766	$ 192,223	$ 576,312	$ 540,496
Point in time
Disaggregation of revenues
Total revenues	89,092		267,021
Over time
Disaggregation of revenues
Total revenues	110,674		309,291
United States
Disaggregation of revenues
Total revenues	146,268		417,927
International
Disaggregation of revenues
Total revenues	53,498		158,385
Commercial
Disaggregation of revenues
Total revenues	159,034		460,180
Government
Disaggregation of revenues
Total revenues	40,732		116,132
Filtration
Disaggregation of revenues
Total revenues	83,067	69,721	228,769	195,531
Filtration | Point in time
Disaggregation of revenues
Total revenues	41,633		115,852
Filtration | Over time
Disaggregation of revenues
Total revenues	41,434		112,917
Filtration | United States
Disaggregation of revenues
Total revenues	69,872		190,701
Filtration | International
Disaggregation of revenues
Total revenues	13,195		38,068
Filtration | Commercial
Disaggregation of revenues
Total revenues	47,482		131,112
Filtration | Government
Disaggregation of revenues
Total revenues	35,585		97,657
Test
Disaggregation of revenues
Total revenues	42,298	45,034	126,459	123,368
Test | Point in time
Disaggregation of revenues
Total revenues	6,485		29,092
Test | Over time
Disaggregation of revenues
Total revenues	35,813		97,367
Test | United States
Disaggregation of revenues
Total revenues	26,923		82,072
Test | International
Disaggregation of revenues
Total revenues	15,375		44,387
Test | Commercial
Disaggregation of revenues
Total revenues	37,980		111,577
Test | Government
Disaggregation of revenues
Total revenues	4,318		14,882
USG
Disaggregation of revenues
Total revenues	52,894	55,489	157,639	157,942
USG | Point in time
Disaggregation of revenues
Total revenues	40,968		122,075
USG | Over time
Disaggregation of revenues
Total revenues	11,926		35,564
USG | United States
Disaggregation of revenues
Total revenues	38,414		112,289
USG | International
Disaggregation of revenues
Total revenues	14,480		45,350
USG | Commercial
Disaggregation of revenues
Total revenues	52,065		154,240
USG | Government
Disaggregation of revenues
Total revenues	829		3,399
Technical Packaging
Disaggregation of revenues
Total revenues	21,507	$ 21,979	63,445	$ 63,655
Technical Packaging | Over time
Disaggregation of revenues
Total revenues	21,507		63,445
Technical Packaging | United States
Disaggregation of revenues
Total revenues	11,559		32,865
Technical Packaging | International
Disaggregation of revenues
Total revenues	9,948		30,580
Technical Packaging | Commercial
Disaggregation of revenues
Total revenues	$ 21,507		63,251
Technical Packaging | Government
Disaggregation of revenues
Total revenues			$ 194