SEGMENT AND GEOGRAPHIC INFORMATION - Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Sep. 30, 2024
SEGMENT INFORMATION
Revenue	$ 130,683	$ 105,786	$ 374,882	$ 360,322
Long-lived assets	182,335		182,335		$ 188,328
United States
SEGMENT INFORMATION
Revenue	116,474	89,707	326,024	303,905
Long-lived assets	161,362		161,362		167,772
Netherlands
SEGMENT INFORMATION
Revenue	6,277	8,545	26,714	36,331
Long-lived assets	7,103		7,103		7,159
Other
SEGMENT INFORMATION
Revenue	7,932	$ 7,534	22,144	$ 20,086
Long-lived assets	$ 13,870		$ 13,870		$ 13,397