SEGMENT INFORMATION - Operating Segments Revenue and Operating Income (Loss) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) segment	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)
SEGMENT INFORMATION
Number of segments | segment			2
Revenue	$ 140,313	$ 18,751	$ 224,524	$ 36,636
Operating Income (Loss)	7,868	(521)	(25,773)	(507)
Interest (expense)	(7,547)	(366)	(12,375)	(713)
Other (expense) income	(139)	179	(57,866)	179
Income (loss) before income taxes	182	(708)	(96,014)	(1,041)
Assets	1,139,421		1,139,421		$ 321,856
United States
SEGMENT INFORMATION
Revenue	117,890	18,751	190,335	36,636
Netherlands
SEGMENT INFORMATION
Revenue	12,119		18,655
Other
SEGMENT INFORMATION
Revenue	10,304		15,534
Intersegment
SEGMENT INFORMATION
Revenue	1,997		2,317
Discovery and Safety Assessment Segment (DSA)
SEGMENT INFORMATION
Revenue	39,054	18,751	71,879	36,636
Operating Income (Loss)	3,752	3,769	9,794	7,046
Assets	262,010		262,010		$ 321,856
Research Models And Services Segment (RMS)
SEGMENT INFORMATION
Revenue	101,259		152,645
Operating Income (Loss)	22,562		22,642
Assets	877,411		877,411
Unallocated Corporate Segment
SEGMENT INFORMATION
Operating Income (Loss)	$ (18,446)	$ (4,290)	$ (58,209)	$ (7,553)