Basis and Summary of Significant Accounting Policies - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accounts Payable	$ 68,419	$ 80,821
Accrued Insurance Costs	40,799	41,680
Accrued Salaries and Benefits	46,834	46,511
Accrued Real Estate and Sales Taxes	33,224	31,054
Deferred Rent	29,535	29,912
Other Accrued Expenses and Liabilities	70,200	74,832
Accounts Payable and Accrued Expenses	$ 289,011	$ 304,810