Business and Summary of Significant Accounting Policies - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Accounts Payable	$ 80,821	$ 71,941
Accrued Insurance Costs	41,680	47,649
Accrued Salaries and Benefits	46,511	41,612
Accrued Real Estate and Sales Taxes	31,054	32,986
Deferred Rent	29,912	31,859
Other Accrued Expenses and Liabilities	74,832	71,719
Accounts Payable and Accrued Liabilities	$ 304,810	$ 297,766