Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 3,760	$ 3,824
Share-based compensation	4,365	9,167
Other accrued compensation	17,037	10,697
Claims reserves	2,241	5,355
Deferred revenue	4,491	4,122
Accrued severance	3,505	1,244
Other non-deductible accrued liabilities	1,224	1,210
Indirect tax benefits	2,247	1,867
Operating lease - right-of-use liabilities	13,564	18,603
Other deferred tax assets	1,962	111
Total deferred tax assets	54,396	56,200
Valuation allowances	(905)	(1,828)
Deferred tax assets after valuation allowances	53,491	54,372
Deferred tax liabilities:
Depreciation	(29,967)	(20,479)
Amortization of goodwill and intangible assets	(15,670)	(12,569)
Operating lease - right-of-use assets	(7,091)	(15,893)
Other deferred tax liabilities	(6,023)	(5,562)
Total deferred tax liabilities	(58,751)	(54,503)
Net deferred tax liabilities	$ (5,260)	$ (131)