Details of Certain Balance Sheet Accounts (Schedule of Prepaid Expenses and Other Current Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Details of Certain Balance Sheet Accounts [Abstract]
Prepaid health insurance	$ 1,393	$ 2,901
Prepaid workers' compensation and liability insurance	837	1,332
Prepaid rent	501	555
Workers' compensation insurance receivable	1,219	543
Other	3,300	3,048
Prepaid expenses and other current assets	$ 7,250	$ 8,379