Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Accounts receivable reserves	$ 829	$ 542
Accrued liabilities	1,657	1,161
Deferred compensation obligation	5,046	4,715
Stock-based compensation	618	739
Operating lease liabilities	5,223	5,497
Pension and post-retirement benefit plans	3,721	3,745
Deferred payroll taxes	4,978	0
Other	461	160
Deferred tax assets	22,533	16,559
Deferred tax liabilities:
Prepaid expenses	(489)	(459)
Fixed assets	(2,811)	(965)
Deferred payroll taxes	(2,370)	(1,889)
ROU assets for operating leases	(4,347)	(4,767)
Partnership basis difference	(1,469)	0
Other	(309)	(328)
Deferred tax liabilities	(11,795)	(8,408)
Valuation allowance	0	(114)
Total Deferred tax assets, net	$ 10,738	$ 8,037