Components of Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance For Doubtful Accounts And Unbilled Services
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of period		$ 185,754	$ 144,825	$ 109,273
Charged to Expense		8,912	15,564	18,252
Charged to Other Accounts	[1]	9,501	42,134	35,423
Deductions	[2]	25,348	16,769	18,123
Balance at End of Period		178,819	185,754	144,825
Valuation Allowance of Deferred Tax Assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of period		13,167	14,442	10,201
Charged to Expense		5,733		4,241
Deductions	[2]		1,275
Balance at End of Period		$ 18,900	$ 13,167	$ 14,442

[1] Includes estimated provision for unbilled services recorded as a reduction to revenues (i.e., fee, rate and other adjustments).

[2] Includes estimated direct write-offs of uncollectible and unrealizable accounts receivable.