Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Cash Flows [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 136,026	$ 210,809	$ 136,026	$ 210,809
CASH FLOWS FROM OPERATING ACTIVITIES:
NET INCOME (LOSS)	2,930	(10,955)	4,171	7,708
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	960	(550)	596
Adjustments:
Amortization	29,459	30,734	60,236	69,427
Accretion	3,886	2,312	7,204	4,552
Deferred income taxes	(1,265)	(3,636)	(811)	(1,052)
Loss on debt extinguishments	0	9,342	0	9,342
Fair value adjustments, net	2,462	(336)	(2,192)	864
Stock-based compensation	1,850	2,235	4,636	5,542
Gain on sale of the Joaquin project	0	0	0	(21,138)
Foreign exchange and other	2,174	(3,421)	2,242	(5,317)
Changes in operating assets and liabilities:
Receivables	(8,888)	(2,215)	(10,579)	3,465
Prepaid expenses and other current assets	8,126	4,061	2,491	(845)
Inventories	(2,766)	(4,809)	(11,474)	10,362
Accounts payable and accrued liabilities	(39,262)	(167)	(41,127)	(15,466)
CASH PROVIDED BY OPERATING ACTIVITIES	(1,294)	24,105	14,247	68,040
Cash provided by (used in) activities of discontinued operations	0	5,175	(2,690)	16,510
Net Cash Provided by (Used in) Operating Activities	(1,294)	29,280	11,557	84,550
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(41,165)	(37,107)	(83,510)	(60,698)
Proceeds from the sale of assets	96	436	156	15,455
Purchase of investments	(39)	(8,948)	(400)	(9,964)
Sales and maturities of short-term investments	11,141	898	12,760	10,918
Other	(33)	(52)	(98)	(66)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations	(30,000)	(44,773)	(71,092)	(44,355)
Cash provided by (used in) activities of discontinued operations	0	(375)	(28,470)	(763)
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(30,000)	(45,148)	(99,562)	(45,118)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of notes and bank borrowings, net of issuance costs	0	244,958	15,000	244,958
Payments on long-term debt, capital leases, and associated costs	(4,373)	(188,910)	(22,822)	(192,116)
Other	(233)	(473)	(4,839)	(3,720)
Cash provided by (used in) activities of continuing operations	(4,606)	55,575	(12,661)	49,122
Cash provided by (used in) activities of discontinued operations	0	(21)	(22)	(41)
Cash provided by (used in) activities of discontinued operations	(4,606)	55,554	(12,683)	49,081
Effect of exchange rate changes on cash and cash equivalents	(175)	328	382	884
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(36,075)	40,014	(100,306)	89,397
Cash and cash equivalents at end of period	123,539	200,979	123,539	200,979
Less net cash provided by (used in) discontinued operations	0	(338)	(32,930)	5,189
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	$ (36,075)	40,352	(67,376)	84,208
Net subsidiary payments to parent company		$ 5	$ 1,748	$ 10,517