BUSINESS COMBINATIONS - Fair Value of Assets Acquired and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Jun. 02, 2021
Intangible assets:
Goodwill	$ 1,000,289	$ 787,972
Landmark Acquisition
Asset Acquisition [Line Items]
Cash			$ 25,645
Other tangible assets			23,403
Intangible assets:
Total intangible assets			709,240
Total identifiable assets acquired			758,288
Accounts payable, accrued expenses and other liabilities			73,215
Net identifiable assets acquired			685,073
Goodwill			417,656
Net assets acquired			1,102,729
Landmark Acquisition | Management contracts
Intangible assets:
Total intangible assets			425,880
Landmark Acquisition | Client relationships
Intangible assets:
Total intangible assets			197,160
Landmark Acquisition | Trade name
Intangible assets:
Total intangible assets			$ 86,200