Accounts Receivable, Net and Significant Balance Sheet Information (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts receivable, net
Accounts receivable	$ 105,044	$ 82,076
Receivables under contractual arrangements	12,961	11,194
Accounts receivable, gross, current	118,005	93,270
Less allowances for doubtful accounts	2,442	2,475
Accounts receivable, net	115,563	90,795
Other current assets
Refundable income taxes	0	2,602
Deferred income taxes	8,815	12,071
Other	2,593	2,247
Total	11,408	16,920
Other assets, noncurrent
Assets invested for self-insurance	10,758	13,064
Investment--cost-method affiliate	1,168	1,168
Deferred income taxes	1,059	0
Other	1,299	1,737
Total	14,284	15,969
Accrued expenses
Employee compensation	17,888	15,046
Accrued compensated absences	7,080	7,138
Self-insured medical claims	2,571	2,950
Customer advances, deposits	1,346	1,321
Income taxes payable	2,013	0
Taxes, other than income	2,463	2,622
Accrued litigation settlement	0	2,900
Other	1,101	2,146
Total	34,462	34,123
Other liabilities, noncurrent
Pension and retirement plans	14,513	11,207
Deferred income taxes	0	5,633
Other	3,367	2,525
Total	$ 17,880	$ 19,365