INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Stock-based compensation	$ 1,330	$ 983
Federal benefit of state uncertain tax positions	563	746
Accrued vacation	618	521
Deferred rent	112	95
Deferred payroll tax	947	0
State net operating loss carryforwards	53	228
Allowance for doubtful accounts	552	311
Right of use lease liability	2,851	2,840
Other	873	465
Gross deferred tax assets	7,899	6,189
Less: Valuation allowance	(4)	(335)
Total deferred tax assets	7,895	5,854
Deferred tax liabilities:
Property and equipment	(1,830)	(2,027)
Capitalized software development costs	(4,423)	(3,544)
Right of use lease asset	(2,739)	(2,746)
Total deferred tax liabilities	(8,992)	(8,317)
Net deferred tax liability	$ (1,097)	$ (2,463)