FAIR VALUE MEASUREMENTS - Estimated Fair Values of Financial Assets and Liabilities Measured on a Recurring Basis (Details) - Fair Value, Inputs, Level 1 - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Deferred compensation liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation liability	$ 2,542	$ 2,475
Deferred compensation asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation asset	$ 1,317	$ 1,156