Accounts Receivable, Net and Supplemental Balance Sheet Information (Tables)

12 Months Ended

Dec. 31, 2016

Accounts Receivable, Net and Supplemental Balance Sheet Information [Abstract]

Schedule of accounts receivable [Table Text Block]

Accounts receivable, net, consisted of the following:

	December 31,
	2016		2015
Accounts receivable	$	128,202	$	104,567
Receivables under contractual arrangements	21,541		19,142
	149,743		123,709
Less allowances for doubtful accounts	3,609		3,708
	$	146,134	$	120,001

Schedule of other current assets [Table Text Block]

The following items comprise the amounts included in the balance sheets:

	December 31,
Other current assets	2016		2015
Refundable income taxes	$	548	$	2,952
Other	1,315		918
Total	$	1,863	$	3,870

Schedule of other assets, noncurrent [Table Text Block]

	December 31,
Other assets, noncurrent	2016		2015
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
Total	$	31,354	$	31,949

Schedule of accrued expenses [Table Text Block]

	December 31,
Accrued expenses	2016		2015
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		—
Taxes, other than income	2,166		3,517
Other	929		935
Total	$	37,659	$	36,146

Schedule of other liabilities, noncurrent [Table Text Block]

	December 31,
Other liabilities, noncurrent	2016		2015
Pension and retirement plans	$	15,982	$	14,296
Other	4,837		3,382
Total	$	20,819	$	17,678