Business and Significant Accounting Policies (Detail) - Property, Equipment and Leasehold Improvements, Less Accumulated Depreciation and Amortization - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Rent expense	$ 38,000	$ 33,800	$ 31,500
Property, equipment and leasehold improvements, gross	306,125	274,370
Less — accumulated depreciation and amortization	(184,519)	(165,637)
Property, equipment and leasehold improvements, net	121,606	108,733
Software
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 166,385	148,195
Software | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	2 years
Software | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	7 years
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 43,137	39,072
Furniture and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Furniture and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	8 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 96,603	$ 87,103
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	2 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	15 years