Supplemental Guarantor Information Condensed Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities, Continuing Operations										$ 197,160	$ 96,461	$ 87,412
Cash Provided by (Used in) Operating Activities, Discontinued Operations										11,296	29,356	26,130
Cash provided by (used in) operating activities		$ 91,811	$ 37,308	$ 24,103	$ 43,938	$ 21,423	$ 39,201	$ 34,752	$ 1,085	208,456	125,817	113,542
Capital expenditures		(47,054)	$ (28,982)	$ (37,107)	(23,591)	(28,134)	$ (22,626)	$ (21,971)	(21,651)	(136,734)	(94,382)	(88,973)
Payments to Acquire Businesses, Net of Cash Acquired										(156,248)	(1,417)	(110,846)
Proceeds from the sale of assets										16,705	16,296	607
Purchase of short term investments and equity securities										(15,058)	(178)	(1,880)
Sales and maturities of short-term investments										11,321	7,077	605
Payments for (Proceeds from) Other Investing Activities										(217)	(4,208)	(4,586)
Payments to Acquire Interest in Subsidiaries and Affiliates										0	0	0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										(280,231)	(76,812)	(205,073)
Cash Provided by (Used in) Investing Activities, Discontinued Operations										(1,392)	(6,631)	(6,220)
CASH USED IN INVESTING ACTIVITIES										(281,623)	(83,443)	(211,293)
Proceeds from Issuance of Unsecured Debt										342,620	0	150,000
Proceeds from Issuance of Common Stock										0	269,556	0
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities										(203,045)	(318,153)	(70,603)
Cash payments on gold production royalty										0	(27,155)	(39,235)
Proceeds From Repayment Intercompany Borrowings										0	0	0
Proceeds from (Payments for) Other Financing Activities										(3,746)	172	(542)
Net Cash Provided by (Used in) Financing Activities, Continuing Operations										135,829	(75,580)	39,620
Cash Provided by (Used in) Financing Activities, Discontinued Operations										(84)	(4,648)	(10,612)
Net Cash Provided by (Used in) Financing Activities										135,745	(80,228)	29,008
Effect of exchange rate changes on cash and cash equivalents										203	(678)	(1,404)
Net Cash Provided by (Used in) Discontinued Operations	[1]									(10,939)	1,576	11,552
CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingNetCashProvidedByUsedInDiscontinuedOperationsAssetsHeldForSale										73,720	(40,108)	(81,699)
Cash and cash equivalents at beginning of period					118,312				158,420	118,312	158,420	240,119
Cash and cash equivalents at end of period		192,032				118,312				192,032	118,312	158,420
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities, Continuing Operations										(8,470)	62,207	(377,091)
Cash Provided by (Used in) Operating Activities, Discontinued Operations										0	0	0
Cash provided by (used in) operating activities										(8,470)	62,207	(377,091)
Capital expenditures										(1,941)	(246)	(514)
Payments to Acquire Businesses, Net of Cash Acquired										(156,248)	0	(110,846)
Proceeds from the sale of assets										8,917	0	0
Purchase of short term investments and equity securities										(15,057)	(178)	(1,880)
Sales and maturities of short-term investments										9,157	501	2
Payments for (Proceeds from) Other Investing Activities										(3,020)	(4,396)	(4,710)
Payments to Acquire Interest in Subsidiaries and Affiliates										(34,419)	(107,855)	282,041
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										(192,611)	(112,174)	164,093
Cash Provided by (Used in) Investing Activities, Discontinued Operations										0	0	0
CASH USED IN INVESTING ACTIVITIES										(192,611)	(112,174)	164,093
Proceeds from Issuance of Unsecured Debt										342,620		150,000
Proceeds from Issuance of Common Stock											269,556
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities										(185,538)	(303,686)	(62,930)
Cash payments on gold production royalty											0	0
Proceeds From Repayment Intercompany Borrowings										(34,359)	(45,850)	(12,232)
Proceeds from (Payments for) Other Financing Activities										(3,746)	172	(542)
Net Cash Provided by (Used in) Financing Activities, Continuing Operations										187,695	11,892	98,760
Cash Provided by (Used in) Financing Activities, Discontinued Operations										0	0	0
Net Cash Provided by (Used in) Financing Activities										187,695	11,892	98,760
Effect of exchange rate changes on cash and cash equivalents										0	0	0
Net Cash Provided by (Used in) Discontinued Operations										0	0	0
CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingNetCashProvidedByUsedInDiscontinuedOperationsAssetsHeldForSale										(13,386)	(38,075)	(114,238)
Cash and cash equivalents at beginning of period					58,048				96,123	58,048	96,123	210,361
Cash and cash equivalents at end of period		44,662				58,048				44,662	58,048	96,123
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities, Continuing Operations										118,667	134,892	86,486
Cash Provided by (Used in) Operating Activities, Discontinued Operations										0	0	0
Cash provided by (used in) operating activities										118,667	134,892	86,486
Capital expenditures										(85,967)	(58,084)	(52,376)
Payments to Acquire Businesses, Net of Cash Acquired										0	0	0
Proceeds from the sale of assets										6,902	4,800	289
Purchase of short term investments and equity securities										(1)	0	0
Sales and maturities of short-term investments										2,164	6,576	532
Payments for (Proceeds from) Other Investing Activities										0	368	234
Payments to Acquire Interest in Subsidiaries and Affiliates										12,911	25,047	20,239
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										(63,991)	(21,293)	(31,082)
Cash Provided by (Used in) Investing Activities, Discontinued Operations										0	0	0
CASH USED IN INVESTING ACTIVITIES										(63,991)	(21,293)	(31,082)
Proceeds from Issuance of Unsecured Debt										0		0
Proceeds from Issuance of Common Stock											0
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities										(7,926)	(10,894)	(7,428)
Cash payments on gold production royalty											0	0
Proceeds From Repayment Intercompany Borrowings										44,540	86,914	19,518
Proceeds from (Payments for) Other Financing Activities										0	0	0
Net Cash Provided by (Used in) Financing Activities, Continuing Operations										(52,466)	(97,808)	(26,946)
Cash Provided by (Used in) Financing Activities, Discontinued Operations										0	0	0
Net Cash Provided by (Used in) Financing Activities										(52,466)	(97,808)	(26,946)
Effect of exchange rate changes on cash and cash equivalents										6	4	(11)
Net Cash Provided by (Used in) Discontinued Operations										0	0	0
CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingNetCashProvidedByUsedInDiscontinuedOperationsAssetsHeldForSale										2,216	15,795	28,447
Cash and cash equivalents at beginning of period					50,023				34,228	50,023	34,228	5,781
Cash and cash equivalents at end of period		52,239				50,023				52,239	50,023	34,228
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities, Continuing Operations										130,491	26,331	53,328
Cash Provided by (Used in) Operating Activities, Discontinued Operations										11,296	29,356	26,130
Cash provided by (used in) operating activities										141,787	55,687	79,458
Capital expenditures										(48,826)	(36,052)	(36,083)
Payments to Acquire Businesses, Net of Cash Acquired										0	(1,417)	0
Proceeds from the sale of assets										886	11,496	318
Purchase of short term investments and equity securities										0	0	0
Sales and maturities of short-term investments										0	0	71
Payments for (Proceeds from) Other Investing Activities										2,803	(180)	(110)
Payments to Acquire Interest in Subsidiaries and Affiliates										(881)	0	120
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										(46,018)	(26,153)	(35,684)
Cash Provided by (Used in) Investing Activities, Discontinued Operations										(1,392)	(6,631)	(6,220)
CASH USED IN INVESTING ACTIVITIES										(47,410)	(32,784)	(41,904)
Proceeds from Issuance of Unsecured Debt										0		0
Proceeds from Issuance of Common Stock											0
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities										(9,581)	(3,573)	(245)
Cash payments on gold production royalty											(27,155)	(39,235)
Proceeds From Repayment Intercompany Borrowings										(9,801)	(13,404)	(27,321)
Proceeds from (Payments for) Other Financing Activities										0	0	0
Net Cash Provided by (Used in) Financing Activities, Continuing Operations										220	(17,324)	(12,159)
Cash Provided by (Used in) Financing Activities, Discontinued Operations										(20,843)	(21,149)	(8,358)
Net Cash Provided by (Used in) Financing Activities										(20,623)	(38,473)	(20,517)
Effect of exchange rate changes on cash and cash equivalents										197	(682)	(1,393)
Net Cash Provided by (Used in) Discontinued Operations										(10,939)	1,576	11,552
CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingNetCashProvidedByUsedInDiscontinuedOperationsAssetsHeldForSale										84,890	(17,828)	4,092
Cash and cash equivalents at beginning of period					10,241				28,069	10,241	28,069	23,977
Cash and cash equivalents at end of period		95,131				10,241				95,131	10,241	28,069
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities, Continuing Operations										(43,528)	(126,969)	324,689
Cash Provided by (Used in) Operating Activities, Discontinued Operations										0	0	0
Cash provided by (used in) operating activities										(43,528)	(126,969)	324,689
Capital expenditures										0	0	0
Payments to Acquire Businesses, Net of Cash Acquired										0	0	0
Proceeds from the sale of assets										0	0	0
Purchase of short term investments and equity securities										0	0	0
Sales and maturities of short-term investments										0	0	0
Payments for (Proceeds from) Other Investing Activities										0	0	0
Payments to Acquire Interest in Subsidiaries and Affiliates										22,389	82,808	(302,400)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										22,389	82,808	(302,400)
Cash Provided by (Used in) Investing Activities, Discontinued Operations										0	0	0
CASH USED IN INVESTING ACTIVITIES										22,389	82,808	(302,400)
Proceeds from Issuance of Unsecured Debt										0		0
Proceeds from Issuance of Common Stock											0
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities										0	0	0
Cash payments on gold production royalty											0	0
Proceeds From Repayment Intercompany Borrowings										380	27,660	(20,035)
Proceeds from (Payments for) Other Financing Activities										0	0	0
Net Cash Provided by (Used in) Financing Activities, Continuing Operations										380	27,660	(20,035)
Cash Provided by (Used in) Financing Activities, Discontinued Operations										20,759	16,501	(2,254)
Net Cash Provided by (Used in) Financing Activities										21,139	44,161	(22,289)
Effect of exchange rate changes on cash and cash equivalents										0	0	0
Net Cash Provided by (Used in) Discontinued Operations										0	0	0
CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingNetCashProvidedByUsedInDiscontinuedOperationsAssetsHeldForSale										0	0	0
Cash and cash equivalents at beginning of period					$ 0				$ 0	0	0	0
Cash and cash equivalents at end of period		$ 0				$ 0				$ 0	$ 0	$ 0

[1] Less net cash provided by (used in) discontinued operations includes the following cash transactions: net subsidiary payments to parent company of $20,759, $16,501 during the years ended December 31, 2017, 2016, respectively, and net parent company payments to subsidiary of $2,254 during the year ended December 31, 2015.