POST EMPLOYMENT BENEFITS - Fair value of total plan assets by asset category (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Fair value of total plan assets by asset category
Total	$ 15,993	$ 14,385	$ 21,269
Cash
Fair value of total plan assets by asset category
Total	431	409
Investment grade corporate bonds
Fair value of total plan assets by asset category
Total	14,184	4,408
Multi-asset fund
Fair value of total plan assets by asset category
Total	1,378	9,568
Level 1
Fair value of total plan assets by asset category
Total	431	409
Level 1 | Cash
Fair value of total plan assets by asset category
Total	431	409
Level 1 | Investment grade corporate bonds
Fair value of total plan assets by asset category
Total	0	0
Level 1 | Multi-asset fund
Fair value of total plan assets by asset category
Total	0	0
Level 2
Fair value of total plan assets by asset category
Total	15,562	13,976
Level 2 | Cash
Fair value of total plan assets by asset category
Total	0	0
Level 2 | Investment grade corporate bonds
Fair value of total plan assets by asset category
Total	14,184	4,408
Level 2 | Multi-asset fund
Fair value of total plan assets by asset category
Total	1,378	9,568
Level 3
Fair value of total plan assets by asset category
Total	0	0
Level 3 | Cash
Fair value of total plan assets by asset category
Total	0	0
Level 3 | Investment grade corporate bonds
Fair value of total plan assets by asset category
Total	0	0
Level 3 | Multi-asset fund
Fair value of total plan assets by asset category
Total		$ 0