Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts and unbilled services
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of period	$ 180,687	$ 178,819	$ 185,754
Charged to Expense	17,872	15,386	8,912
Charged to Other Accounts	25,300	9,656	9,501
Deductions	21,465	23,174	25,348
Balance at End of Period	202,394	180,687	178,819
Valuation allowance for deferred tax asset
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of period	21,621	18,900	13,167
Charged to Expense	308	2,721	5,733
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Period	$ 21,929	$ 21,621	$ 18,900

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

+ Details

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- Definition

Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

+ References

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- Definition

Amount of increase in valuation and qualifying accounts and reserves from charge to accounts other than cost and expense.

+ References

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Amount of decrease in valuation and qualifying accounts and reserves.

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