Accrued Payroll Costs And Retirement Obligations (Accrued Payroll Costs And Retirement Obligations) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Accrued Payroll Costs And Retirement Obligations [Abstract]
Payroll and benefits	$ 185,471	$ 181,035
Employee retirement obligations	86,719	87,031
Workers' compensation	25,954	24,217
Payroll taxes	32,632	63,011
Total accrued payroll costs and retirement obligations	$ 330,776	$ 355,294