Accrued Payroll and Benefit Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Payroll and benefits	$ 243,301	$ 240,793
Employee deferred compensation plans	252,349	212,220
Workers’ compensation	19,361	25,834
Payroll taxes	24,037	25,935
Accrued payroll and benefit costs	539,048	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	$ 83,899	$ 81,874