Description of Business and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of reportable business segments | segment	5
Research and development costs related to software development	$ 14,900	$ 17,500	$ 19,500
Advertising costs	14,800	15,900	18,200
Provision for doubtful accounts	$ 15,386	8,912	15,564
Forgivable loans, forgiveness period, minimum	1 year
Forgivable loans, forgiveness period, maximum	10 years
Definite-lived intangible assets amortization period	13 years 7 months 6 days
Unamortized capitalized software cost	$ 14,800	16,600
Amortization of capitalized software cost	6,700	12,000	$ 6,500
Deferred rent	$ 43,900	$ 41,900
Minimum
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Definite-lived intangible assets amortization period	1 year
Maximum
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Definite-lived intangible assets amortization period	15 years
Lease provisions for renewal options (In years)	5 years
Furniture, Equipment, And Internal-Use Software | Minimum
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful of furniture, equipment and internal use software (in years)	3 years
Furniture, Equipment, And Internal-Use Software | Maximum
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful of furniture, equipment and internal use software (in years)	7 years
Software and Software Development Costs
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful of furniture, equipment and internal use software (in years)	3 years
Geographic Concentration Risk | Consolidated Revenues | Non U.S
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Revenue from the work of professionals	30.00%