Self-Insurance Accruals (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Self-Insurance Accruals [Abstract]
Workers' compensation			$ 41,577	$ 40,764
Present value discount			3,099	2,346
Workers' Compensation, Net of Discount			38,478	38,418
Vehicle liability			13,342	5,536
General liability			31,965	23,740
Total	$ 67,694	$ 62,838	83,785	67,694
Less current portion			27,434	23,782
Noncurrent portion			$ 56,351	$ 43,912
Loss contingency accrual [Roll Forward]
Balance, beginning of year	67,694	62,838
Provision for claims	51,685	34,884
Payment of claims	(35,594)	(30,028)
Balance, end of year	$ 83,785	$ 67,694
Workers' compensation discount rate	2.50%	2.00%