Accounts Receivable, Net and Supplemental Balance Sheet Information Accounts Receivable, Net and Supplemental Balance Sheet Information(Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, net
Accounts receivable	$ 128,202	$ 104,567
Receivables under contractual arrangements	21,541	19,142
Accounts receivable, gross, current	149,743	123,709
Less allowances for doubtful accounts	3,609	3,708
Accounts receivable, net	146,134	120,001
Other current assets
Refundable income taxes	548	2,952
Other	1,315	918
Other current assets, total	1,863	3,870
Other assets, noncurrent
Assets invested for self-insurance	15,492	17,167
Investment--cost-method affiliate	1,168	1,172
Deferred income taxes	11,129	11,521
Other	3,565	2,089
Other assets, noncurrent, total	31,354	31,949
Accrued expenses
Employee compensation	18,438	18,176
Accrued compensated absences	9,215	8,607
Self-insured medical claims	2,961	2,347
Customer advances, deposits	2,997	2,564
Income taxes payable	953	0
Taxes, other than income	2,166	3,517
Other	929	935
Accrued expenses, total	37,659	36,146
Other liabilities, noncurrent
Pension and retirement plans	15,982	14,296
Other	4,837	3,382
Other liabilities, noncurrent, total	$ 20,819	$ 17,678