Business Acquisitions - Summary of Purchase Price Attributable to Acquisitions (Details) - USD ($) $ in Thousands	Jan. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Cash		$ 1,527
Accounts receivable		17,059
Other current assets		1,265
Current assets		19,851
Property and equipment		7,117
Goodwill		147,609
Total assets		253,586
Current liabilities		9,721
Total liabilities		9,721
Purchase price		243,865
Customer Relationships
Business Acquisition [Line Items]
Intangible assets		56,000
Trade Names
Business Acquisition [Line Items]
Intangible assets		4,200
Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets		4,109
Proprietary Software
Business Acquisition [Line Items]
Intangible assets		14,700
MSE Group
Business Acquisition [Line Items]
Cash	$ 2,810
Accounts receivable	3,068
Other current assets	31
Current assets	5,909
Property and equipment	513
Goodwill	7,532
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
All Other Acquisitions
Business Acquisition [Line Items]
Property and equipment		75
Goodwill		626
Total assets		810
Purchase price		810
All Other Acquisitions \| Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets		$ 109

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