Acquisitions - Assets and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Nov. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Consideration
Goodwill	$ 852,536		$ 831,800	$ 830,252
Employment Background Investigations, Inc.
Consideration
Cash		$ 0
Accounts receivable		8,861
Prepaid expenses		394
Property and equipment		1,290
Intangible assets		59,161
Total assets acquired		69,706
Accounts payable and accrued expenses		5,614
Other current liabilities		1,182
Deferred tax liability		16,566
Other liabilities		298
Total liabilities assumed		23,660
Total identifiable net assets		46,046
Goodwill		21,721
Total consideration		$ 67,767