Accounts Receivable, Net and Supplemental Balance-Sheet Information (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Accounts Receivable, Net and Supplemental Balance Sheet Information [Abstract]
Accounts receivable	$ 87,399	$ 82,076
Receivables under contractual arrangements	21,538	11,194
Accounts receivable, gross, current	108,937	93,270
Less allowances for doubtful accounts	2,657	2,475
Accounts receivable, net	106,280	90,795
Prepaid Expense and Other Assets, Current [Abstract]
Refundable income taxes	2,884	2,602
Deferred income taxes	7,927	12,071
Prepaid expenses	5,999	6,968
Other	619	2,247
Total	17,429	23,888
Accrued Liabilities [Abstract]
Employee compensation	13,190	15,046
Accrued compensated absences	8,158	7,138
Self-insured medical claims	3,148	2,950
Customer advances, deposits	0	1,321
Taxes, other than income	2,771	2,622
Accrued litigation settlement	2,900	2,900
Other	2,769	2,146
Total	$ 32,936	$ 34,123