Accrued Payroll Costs And Retirement Obligations (Accrued Payroll Costs And Retirement Obligations) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accrued Payroll Costs And Retirement Obligations [Abstract]
Payroll and benefits	$ 181,035	$ 153,329
Employee retirement obligations	87,031	80,716
Workers' compensation	24,217	24,136
Payroll taxes	63,011	56,466
Total accrued payroll costs and retirement obligations	$ 355,294	$ 314,647