Accrued Payroll and Benefit Costs (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Payroll and benefits	$ 276,904	$ 240,793
Employee deferred compensation plans	237,628	212,220
Workers’ compensation	27,213	25,834
Payroll taxes	19,453	25,935
Accrued payroll and benefit costs	561,198	504,782
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	$ 82,923	$ 81,874