Accrued Payroll and Benefit Costs (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Payroll and benefits	$ 240,793	$ 213,962
Employee deferred compensation plans	212,220	181,709
Workers’ compensation	25,834	26,127
Payroll taxes	25,935	26,317
Accrued payroll and benefit costs	504,782	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	$ 81,874	$ 79,060