Commitments and Contingencies Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Operating Leases, Rent Expense	$ 32,700	$ 26,400	$ 25,600
Deferred Rent Credit, Current	1,300	1,200
Deferred Rent Credit, Noncurrent	5,600	5,000
Costs and Expenses, Related Party	1,269	1,269	$ 1,269
Self Insurance Reserve	2,400	2,100
Workers' compensation receivable	15,011	$ 12,702
Letters of Credit Outstanding, Amount	$ 4,400