Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts Payable and Accrued Liabilities, Current [Abstract]
Salaries and wages	$ 91,784	$ 102,025
Insurance reserves	63,309	71,123
Vacation	40,281	42,411
Real estate taxes	30,743	34,002
Interest	13,745	12,948
Lease payable	11,942	11,211
Accrued utilities	10,807	10,582
Taxes payable	2,636	2,818
Other	64,719	40,917
Total	$ 329,966	$ 328,037