Accounts Receivable, Net and Supplemental Balance-Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, net
Accounts receivable	$ 110,712	$ 143,244
Receivables under contractual arrangements	51,852	29,895
Accounts receivable, gross	162,564	173,139
Less allowances for doubtful accounts	4,486	4,468
Accounts receivable, net	158,078	168,671
Other current assets
Refundable income taxes	1,229	587
Prepaid expense	13,735	15,893
Other	189	784
Total	15,153	17,264
Accrued expenses
Employee compensation	12,010	20,794
Accrued compensated absences	9,590	9,267
Self-insured medical claims	4,447	3,193
Income tax payable	623	3,443
Customer advances, deposits	72	1,672
Taxes, other than income	3,662	2,279
Other	1,908	2,168
Total	32,312	42,816
Other current liabilities
Short-term Non-bank Loans and Notes Payable	0	149
Current portion of long-term debt	13,155	16,817
Current portion of self-insurance accruals	23,846	23,782
Total	$ 37,001	$ 40,748