Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 47,612	$ 38,268
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(21,000)	(16,150)
Property, Plant and Equipment, Net	26,612	22,118
Depreciation Expense	6,800	5,900	$ 5,600
Office furnishings, leasehold improvements, computer equipment and computer software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	37,567	28,207
Transportation and construction equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 10,045	$ 10,061