Valuation and Qualifying Accounts - Summary of Allowances for Doubtful Accounts and Unbilled Services and Valuation Allowance for Deferred Tax Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowances for doubtful accounts and unbilled services [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 21,306	$ 18,668	$ 22,241
Additions	9,852	63,268	69,979
Deductions	15,363	60,630	73,552
Ending balance	15,795	21,306	18,668
Valuation allowance for deferred tax assets [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	2,112	1,016	3,143
Additions	1,090	1,160	1
Deductions	326	64	2,128
Ending balance	$ 2,876	$ 2,112	$ 1,016