Business Acquisitions - Summary of Purchase Price Attributable to Acquisitions (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Cash	$ 3,230	$ 1,527
Accounts receivable	4,022	17,059
Other current assets	375	1,265
Current assets	7,627	19,851
Property and equipment	1,489	7,117
Goodwill	12,627	147,609
Total assets	35,086	253,586
Current liabilities	1,283	9,721
Total liabilities	1,283	9,721
Purchase price	33,803	243,865
Customer Relationships
Business Acquisition [Line Items]
Intangible assets	10,376	56,000
Trade Names
Business Acquisition [Line Items]
Intangible assets	1,805	4,200
Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets	1,162	4,109
Proprietary Software
Business Acquisition [Line Items]
Intangible assets		14,700
Vista
Business Acquisition [Line Items]
Cash	420
Accounts receivable	1,035
Other current assets	344
Current assets	1,799
Property and equipment	976
Goodwill	5,014
Total assets	10,969
Current liabilities	469
Total liabilities	469
Purchase price	10,500
Vista | Customer Relationships
Business Acquisition [Line Items]
Intangible assets	1,656
Vista | Trade Names
Business Acquisition [Line Items]
Intangible assets	1,284
Vista | Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets	240
MSE Group
Business Acquisition [Line Items]
Cash	2,810
Accounts receivable	2,987
Other current assets	31
Current assets	5,828
Property and equipment	513
Goodwill	7,613
Total assets	24,117
Current liabilities	814
Total liabilities	814
Purchase price	23,303
MSE Group | Customer Relationships
Business Acquisition [Line Items]
Intangible assets	8,720
MSE Group | Trade Names
Business Acquisition [Line Items]
Intangible assets	521
MSE Group | Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets	$ 922
CTEH
Business Acquisition [Line Items]
Cash		1,527
Accounts receivable		17,059
Other current assets		1,265
Current assets		19,851
Property and equipment		7,042
Goodwill		146,983
Total assets		252,776
Current liabilities		9,721
Total liabilities		9,721
Purchase price		243,055
CTEH | Customer Relationships
Business Acquisition [Line Items]
Intangible assets		56,000
CTEH | Trade Names
Business Acquisition [Line Items]
Intangible assets		4,200
CTEH | Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets		4,000
CTEH | Proprietary Software
Business Acquisition [Line Items]
Intangible assets		14,700
Other 2020 Acquisitions
Business Acquisition [Line Items]
Property and equipment		75
Goodwill		626
Total assets		810
Purchase price		810
Other 2020 Acquisitions | Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets		$ 109