Business Acquisitions - Summary of Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Aug. 27, 2021	Dec. 31, 2020
Fair Values of Assets Acquired and Liabilities Assumed
Goodwill	$ 791,902		$ 345,184
Drum Parent, Inc.
Fair Values of Assets Acquired and Liabilities Assumed
Cash and cash equivalents		$ 1,900
Accounts receivable		69,100
Contract assets		40,100
Income taxes receivable, net		700
Right of use assets under operating leases		1,500
Prepaid expenses		5,200
Property and equipment		118,100
Intangible assets		335,000
Goodwill		446,800
Total assets acquired		1,018,400
Trade and other payables		46,200
Finance lease obligations		27,500
Contract liabilities		12,700
Operating lease obligations		1,500
Other liabilities		5,300
Deferred tax liabilities		94,800
Total liabilities assumed		188,000
Net assets acquired		$ 830,400