Consolidated Statements of Cash Flow - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net income	$ 22,284	$ 21,798	$ 23,169
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	47,284	44,677	40,970
Amortization	2,306	2,214	2,070
Gain on sale of assets	(4,664)	(2,026)	(806)
Deferred income taxes	60	(2,975)	(2,679)
Other	1,286	2,399	(5,638)
Changes in operating assets and liabilities:
Accounts receivable	(26,133)	(8,403)	(4,489)
Accounts payable and accrued expenses	2,454	1,722	1,206
Self-insurance accruals	2,499	1,446	2,116
Other assets, net	7,994	1,837	(6,640)
Adjustments to reconcile net income to net cash provided by operating activities	33,086	40,891	26,110
Net cash provided by operating activities	55,370	62,689	49,279
Capital expenditures:
Equipment	(54,147)	(52,466)	(46,228)
Land and buildings	(2,499)	(3,581)	(9,503)
Proceeds from sales of property and equipment	5,635	2,650	1,366
Purchases of businesses	(3,797)	(2,649)	(9,695)
Net cash used in investing activities	(54,808)	(56,046)	(64,060)
Financing activities
Revolving credit facility borrowings/(payments), net	12,500	10,000	24,500
Borrowings/(payments) of notes payable	656	6,720	(1,091)
Borrowings/(payments) of long-term debt and capital leases	(5,142)	(6,624)	5,695
Purchase of common shares for treasury	(25,290)	(25,395)	(19,598)
Sale of common shares from treasury	11,019	9,328	8,762
Cash received on common-share subscriptions	1,133	1,494	1,741
Dividends	(2,597)	(2,663)	(2,674)
Net cash (used in) provided by financing activities	(7,721)	(7,140)	17,335
Effect of exchange rate changes on cash	135	(1,888)	0
(Decrease) Increase in cash	(7,024)	(2,385)	2,554
Cash, beginning of year	16,030	18,415	15,861
Cash, end of year	$ 9,006	$ 16,030	$ 18,415