CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 4,844	$ 20,909	$ 7,605	$ 29,387
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	22,603	21,384	64,870	64,602
Provision for doubtful accounts			3,796	4,199
Amortization of debt discount and debt issuance costs			420	591
Stock-based compensation	1,548	1,393	4,881	5,071
Deferred income taxes			(6,287)	(3,062)
Loss on non-controlling equity investment			2,131
(Gain) Loss on disposition of long-lived assets	132	(13,496)	321	(15,509)
Unrealized loss on foreign currency			233	1,951
Other non-cash activity			28	246
Changes in operating assets and liabilities, excluding the effects of acquisitions and dispositions:
Accounts receivable			(10,193)	(7,257)
Materials and supplies, prepayments, and other current assets			(5,507)	(715)
Prepaid income taxes			5,158	3,147
Accounts payable and accrued liabilities, advance payments and deposits and other current liabilities			6,324	6,926
Accrued taxes			(19,047)	7,410
Other assets			(2,041)	139
Other liabilities			4,155	888
Net cash provided by operating activities			56,847	98,014
Cash flows from investing activities:
Capital expenditures			(49,363)	(75,375)
Hurricane rebuild capital expenditures			(123)	(78,903)
Hurricane insurance proceeds				34,606
Receipt of government grants				5,400
Divestiture of businesses, net of transferred cash of $0.0				926
Purchase of other investments			(10,285)	(3,000)
Proceeds from sale of assets				4,130
Purchase of short-term investments			(8,028)
Sale of short-term investments			5,141	6,564
Net cash used in investing activities			(62,658)	(105,652)
Cash flows from financing activities:
Dividends paid on common stock			(8,160)	(8,153)
Distributions to non-controlling interests			(5,760)	(15,271)
Payment of debt issuance costs			(1,340)
Principal repayments of term loan			(2,825)	(5,723)
Proceeds from stock option exercises				72
Stock-based compensation share repurchases			(1,607)	(2,101)
Purchases of common stock- share repurchase plan			(162)	(1,576)
Repurchases of non-controlling interests			(1,353)	(5,196)
Investments made by minority shareholders in consolidated affiliates			488
Net cash used in financing activities			(20,719)	(37,948)
Effect of foreign currency exchange rates on cash and cash equivalents			(26)	(353)
Net change in cash, cash equivalents, and restricted cash			(26,556)	(45,939)
Total cash, cash equivalents, and restricted cash, beginning of period			192,907	219,890	$ 219,890
Total cash, cash equivalents, and restricted cash, end of period	$ 166,351	$ 173,951	166,351	173,951	$ 192,907
Noncash investing activity:
Transfer from inventory, materials and supplies to property, plant and equipment				6,708
Purchases of property, plant and equipment included in accounts payable and accrued expenses			$ 7,419	$ 13,202