ACQUISITIONS - Narrative (Details) $ in Thousands		1 Months Ended		3 Months Ended	4 Months Ended	6 Months Ended
	Jun. 01, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($) office_building	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Business Acquisition [Line Items]
Cash paid for business acquisition						$ 131,617	$ 75,482
Contingent consideration, noncurrent		$ 37,014		$ 37,014	$ 37,014	37,014
United Kingdom Office Space Asset Acquisition
Business Acquisition [Line Items]
Number of office buildings acquired | office_building			2
Cash consideration			$ 72,908
Nordeus Limited
Business Acquisition [Line Items]
Percentage of noncontrolling interest	5.50%
Nordeus Limited
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired	94.50%
Cash paid for business acquisition	$ 120,488
Business combination, contingent consideration arrangements, range of outcomes, value, high	$ 153,000
Call option		$ 12,375
Consideration					289,774
Contingent earn-out					$ 61,055
Transaction costs				$ 2,949		$ 4,952
Nordeus Limited | Performance Period One
Business Acquisition [Line Items]
Performance period	12 months
Nordeus Limited | Performance Period Two
Business Acquisition [Line Items]
Performance period	24 months