Accrued Payroll and Benefit Costs (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Payroll and benefits	$ 233,694	$ 213,962
Employee deferred compensation plans	191,671	181,709
Workers’ compensation	27,477	26,127
Payroll taxes	28,816	26,317
Total accrued payroll costs and retirement obligations	481,658	448,115
Chief Executive Officer
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation plan and other benefits related to the Company’s Chief Executive Officer	$ 79,953	$ 79,060