Basis and Summary of Significant Accounting Policies - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accounts Payable	$ 62,314	$ 80,821
Accrued Insurance Costs	39,859	41,680
Accrued Salaries and Benefits	41,903	46,511
Accrued Real Estate and Sales Taxes	31,599	31,054
Deferred Rent	27,816	29,912
Other Accrued Expenses and Liabilities	67,472	74,832
Accounts Payable and Accrued Expenses	$ 270,963	$ 304,810