Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 24,244	$ 40,001	$ 45,370
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	36,702	34,873	33,053
Gain on sale of marketable equity securities	(412)	(347)
Other-than-temporary impairment of marketable securities		230
Loss on disposal of property and equipment	161	239	233
Amortization of debt issuance costs	312	648	693
Write-off of debt issuance costs		1,272
Stock-based compensation	571	494	1,485
Provision for doubtful accounts	3,099	3,004	3,504
Deferred income taxes	6,610	478	1,433
Change in assets and liabilities:
Trade and other accounts receivable	(7,510)	4,424	(19,857)
Prepaid income taxes, prepaid expenses and other assets	(12,748)	4,347	984
Accounts payable, accrued expenses, insurance and claims and other current liabilities	18,003	(11,695)	13,027
Due to/from affiliates, net	595	83	(1)
Other long-term liabilities	(998)	253	(532)
Net cash provided by operating activities	68,629	78,304	79,392
Cash flows from investing activities:
Capital expenditures	(97,351)	(26,257)	(59,784)
Proceeds from the sale of property and equipment	2,426	816	1,326
Purchases of marketable securities	(17)	(1,159)	(2,063)
Proceeds from sale of marketable securities	866	441
Acquisitions of businesses			(2,648)
Net cash used in investing activities	(94,076)	(26,159)	(63,169)
Cash flows from financing activities:
Proceeds from borrowing - revolving debt	220,633	172,758	135,019
Repayments of debt - revolving debt	(217,368)	(161,293)	(135,149)
Proceeds from borrowing - term debt	99,534	163,578	2,500
Repayments of debt - term debt	(78,520)	(175,428)	(4,572)
Dividends paid	(7,954)	(8,171)	(8,409)
Payment of capital lease obligations	(1,789)	(1,050)	(1,349)
Purchases of treasury stock	(26)	(35,065)	(5,631)
Capitalized financing costs	(396)	(1,499)
Net cash provided by (used in) financing activities	14,114	(46,170)	(17,591)
Effect of exchange rate changes on cash and cash equivalents	158	(1,046)	(854)
Net (decrease) increase in cash	(11,175)	4,929	(2,222)
Cash and cash equivalents – beginning of period	12,930	8,001	10,223
Cash and cash equivalents – end of period	1,755	12,930	8,001
Supplemental cash flow information:
Cash paid for interest	7,802	7,649	7,379
Cash paid for income taxes	20,896	$ 21,541	20,833
Acquisition of businesses:
Fair value of assets acquired, net of cash			1,270
Payment of acquisition obligations			1,378
Net cash paid for acquisition of businesses			$ 2,648
Non-cash investing and financing activities
Non-cash capital expenditures pursuant to promissory note.	$ 3,700