BASIS OF PRESENTATION (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020
Noncontrolling Interest [Line Items]
Accounting Standards Update	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Decrease in retained earnings	$ (2,213,053)	$ (2,159,396)
Decrease in accounts receivable trade, net	(396,897)	(466,357)
Decrease in contract assets	(26,236)	(29,570)
Increase to deferred tax assets	$ 893,256	911,565
Adjustment
Noncontrolling Interest [Line Items]
Decrease in retained earnings		2,500
Decrease in accounts receivable trade, net		3,000
Decrease in contract assets		300
Increase to deferred tax assets		$ 800
OT South Africa
Noncontrolling Interest [Line Items]
Ownership percentage by Open Text	70.00%
GXS Singapore
Noncontrolling Interest [Line Items]
Ownership percentage by Open Text	81.00%