Acquisitions (Details) - USD ($) $ in Thousands		6 Months Ended
	Apr. 01, 2020	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Consideration transferred:
Total consideration transferred		$ 2,600
Recognized amounts of identifiable assets acquired and liabilities assumed:
Goodwill			$ 420,782	$ 332,447	$ 235,182
TAS Energy
Consideration transferred:
Cash paid at closing	$ 105,950
Working capital adjustment	39,715
Notes issued to former owners	14,000
Estimated fair value of contingent earn-out payments	9,100
Total consideration transferred	168,765
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents	47,460
Billed and unbilled accounts receivable	18,702
Other current assets	15,634
Other long-term assets	935
Property and equipment	7,709
Goodwill	73,409
Identifiable intangible assets	53,400
Lease right-of-use asset	19,736
Accounts payable	(16,453)
Billings in excess of costs and estimated earnings	(24,196)
Current lease liabilities	(2,337)
Accrued expenses and other current liabilities	(4,849)
Long-term lease liabilities	(17,398)
Other long-term liabilities	(2,987)
Total assets acquired and liabilities assumed	$ 168,765