Consolidated Statements of Cash Flow - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net income	$ 27,977	$ 22,120	$ 22,284
Adjustments to reconcile net income to net cash provided by operating activities net of assets/liabilities acquired:
Depreciation	54,914	50,702	47,284
Amortization	2,055	2,384	2,306
Gain on sale of assets	(5,106)	(3,989)	(4,664)
Deferred income taxes	4,014	3,753	60
Other	134	2,581	1,286
Changes in operating assets and liabilities:
Accounts receivable	(26,829)	(20,784)	(26,133)
Accounts payable and accrued expenses	(1,970)	6,164	2,454
Self-insurance accruals	16,091	4,856	2,499
Other assets, net	(9,176)	(11,011)	7,994
Adjustments to reconcile net income to net cash provided by operating activities	34,127	34,656	33,086
Net cash provided by operating activities	62,104	56,776	55,370
Capital expenditures:
Equipment	(58,620)	(53,128)	(54,147)
Land and buildings	(1,790)	(3,972)	(2,499)
Proceeds from sales of property and equipment	7,494	5,034	5,635
Purchases of businesses, net of cash acquired	(8,461)	(7,452)	(3,797)
Net cash used in investing activities	(61,377)	(59,518)	(54,808)
Financing activities
Revolving credit facility borrowings	507,500	328,000	252,500
Revolving credit facility payments	(514,000)	(295,000)	(240,000)
Proceeds from notes payable	74,716	16,610	17,832
Payments of notes payable	(26,339)	(23,008)	(20,638)
Payments of capital leases	(891)	(2,294)	(1,680)
Purchase of common shares for treasury	(51,116)	(30,404)	(25,290)
Sale of common shares from treasury	20,536	13,820	11,019
Cash received on common-share subscriptions	1,046	1,199	1,133
Dividends	(2,387)	(2,513)	(2,597)
Net cash provided by (used in) financing activities	9,065	6,410	(7,721)
Effect of exchange rate changes on cash	(252)	447	135
Increase (Decrease) in cash	9,540	4,115	(7,024)
Cash, beginning of year	13,121	9,006	16,030
Cash, end of year	$ 22,661	$ 13,121	$ 9,006