PENSION PLANS AND OTHER POST RETIREMENT BENEFITS - Schedule of the Change in Benefit Obligation (Details) - Pension Plan - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation—beginning of fiscal year	$ 67,699	$ 67,226	$ 67,226
Service cost	565	598	2,501
Interest cost	325	306	1,338
Benefits paid	(590)		(1,846)
Actuarial (gain) loss	1,279		(4,947)
Foreign exchange (gain) loss	(1,257)		3,427
Benefit obligation—end of period	68,021		67,699
Less: Current portion	(2,001)		(1,980)
Non-current portion of benefit obligation	66,020		65,719
CDT
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation—beginning of fiscal year	32,865	32,851	32,851
Service cost	94	116	473
Interest cost	112	124	505
Benefits paid	(203)		(800)
Actuarial (gain) loss	406		(1,976)
Foreign exchange (gain) loss	(529)		1,812
Benefit obligation—end of period	32,745		32,865
Less: Current portion	(881)		(880)
Non-current portion of benefit obligation	31,864		31,985
GXS GER
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation—beginning of fiscal year	23,861	24,105	24,105
Service cost	43	51	206
Interest cost	80	89	364
Benefits paid	(256)		(1,027)
Actuarial (gain) loss	320		(1,118)
Foreign exchange (gain) loss	(385)		1,331
Benefit obligation—end of period	23,663		23,861
Less: Current portion	(1,038)		(1,058)
Non-current portion of benefit obligation	22,625		22,803
GXS PHP
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation—beginning of fiscal year	10,973	10,270	10,270
Service cost	428	431	1,822
Interest cost	133	$ 93	469
Benefits paid	(131)		(19)
Actuarial (gain) loss	553		(1,853)
Foreign exchange (gain) loss	(343)		284
Benefit obligation—end of period	11,613		10,973
Less: Current portion	(82)		(42)
Non-current portion of benefit obligation	$ 11,531		$ 10,931

Amount of liability, recognized in statement of financial position, for defined benefit pension plan, classified as current. Excludes other postretirement benefit plan.

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Amount of liability, recognized in statement of financial position, for defined benefit pension plan, classified as noncurrent. Excludes other postretirement benefit plan.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of foreign currency translation gain (loss) which (increases) decreases benefit obligation of defined benefit plan.

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