Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts and unbilled services
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 202,394	$ 180,687	$ 178,819
Charged to Expense	19,602	17,872	15,386
Charged to Other Accounts	56,238	25,300	9,656
Deductions	12,734	21,465	23,174
Balance at End of Period	265,500	202,394	180,687
Valuation allowance for deferred tax asset
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	21,929	21,621	18,900
Charged to Expense	0	308	2,721
Charged to Other Accounts	0	0	0
Deductions	2,064	0	0
Balance at End of Period	$ 19,865	$ 21,929	$ 21,621