Income Taxes - Summary of Net Deferred Tax Assets and (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred income tax assets:
Self insurance reserves	$ 2,138	$ 4,091
Contract loss reserves	541	703
Stock-based awards	1,633	1,300
Bonus	8,373	6,173
Accrued vacation	1,977	1,741
Accrued profit sharing	2,665	2,476
Operating lease liabilities	5,404	5,715
Non-U.S. operating loss	2,520	3,601
Other	2,628	4,661
Total deferred income tax assets before valuation allowances	27,879	30,461
Less: valuation allowances	(2,593)	(2,566)
Total deferred income tax assets	25,286	27,895
Deferred income tax liabilities:
Property and equipment — tax over book depreciation	(36,856)	(34,439)
Intangible assets — tax over book amortization	(2,913)	(2,207)
Right-of-use operating lease assets	(5,398)	(5,702)
Non-U.S. deferred income tax liabilities	0	(1,322)
Contract revenue adjustment	(4,526)	(2,128)
Other	(213)	(436)
Total deferred income tax liabilities	(49,906)	(46,234)
Net deferred income taxes	$ (24,620)	$ (18,339)