Business Combinations - Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 27, 2020	Mar. 06, 2020	Sep. 27, 2019	Jun. 12, 2019
Assets
Goodwill	$ 5,596,156		$ 5,432,544
Wood Group
Assets
Cash and cash equivalents		$ 24,300
Receivables		66,400
Other current assets		5,200
Property, equipment and improvements, net		7,300
Goodwill		205,800
Identifiable intangible assets		81,000
Miscellaneous		5,600
Total Assets		395,600
Liabilities
Accounts payable, accrued expenses and other current liabilities		69,200
Long term liabilities		15,500
Total Liabilities		84,700
Net assets acquired		$ 310,900
KeyW
Assets
Cash and cash equivalents				$ 29,100
Receivables				80,100
Inventories, net				21,300
Prepaid expenses and other				2,500
Property, equipment and improvements, net				24,600
Deferred tax asset and other				35,600
Goodwill				614,200
Identifiable intangible assets				179,000
Total Assets				986,400
Liabilities
Accounts payable, accrued expenses and other current liabilities				8,300
Accrued expenses				68,700
Short term debt				298,400
Other current liabilities				3,900
Other non-current liabilities				2,900
Total Liabilities				382,200
Net assets acquired				$ 604,200