Consolidated Statements of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Other Comprehensive Income [Abstract]
Sales of metal	$ 168,847	$ 200,825	$ 204,525	$ 171,797	$ 205,929	$ 230,593	$ 254,406	$ 204,564	$ 745,994	$ 895,492	$ 1,021,200
Production costs applicable to sales	(100,227)	(131,728)	(142,924)	(88,784)	(106,473)	(124,365)	(131,182)	(92,542)	(463,663)	(454,562)	(419,547)
Amortization	(63,916)	(60,874)	(57,653)	(50,436)	(52,397)	(52,844)	(61,024)	(52,592)	(232,879)	(218,857)	(224,500)
Gross profit									49,452	222,073	377,153
COSTS AND EXPENSES
Administrative and general									55,343	32,977	31,379
Exploration	5,440	3,305	6,774	6,841	6,441	6,957	6,305	6,567	22,360	26,270	19,128
Litigation settlement			(32,000)						32,046	0	0
Write-downs									772,993	5,825	0
Pre-development, care, maintenance and other									11,869	1,261	19,441
Total cost and expenses									894,611	66,333	69,948
OPERATING INCOME									(845,159)	155,740	307,205
OTHER INCOME AND EXPENSE
Loss on debt extinguishments									0	(1,036)	(5,526)
Fair value adjustments, net									82,768	(23,487)	(52,050)
Impairment of marketable securities									(18,308)	(605)	0
Interest and other income									13,323	15,041	(6,610)
Interest expense, net of capitalized interest									(41,303)	(26,169)	(34,774)
Total other income and expense									36,480	(36,256)	(98,960)
Income before income taxes									(808,679)	119,484	208,245
Income tax benefit (expense)									158,116	(70,807)	(114,746)
NET INCOME (LOSS)	(581,528)	(46,265)	(35,040)	12,270	37,550	(15,821)	22,973	3,975	(650,563)	48,677	93,499
Other Comprehensive Income (Loss), Net of Tax:
Unrealized gain (loss) on available for sale securities									(8,489)	(3,351)	(4,975)
Reclassification adjustments for other than temporary impairment of marketable securities									11,221	605	0
Reclassification adjustments for realized loss on sale of marketable securities									83	0	0
Other comprehensive income (loss)									2,815	(2,746)	(4,975)
COMPREHENSIVE INCOME									$ (647,748)	$ 45,931	$ 88,524
BASIC AND DILUTED INCOME PER SHARE
Basic (in dollars per share)	$ (5.77)	$ (0.46)	$ (0.35)	$ 0.14	$ 0.42	$ (0.18)	$ 0.26	$ 0.04	$ (6.65)	$ 0.54	$ 1.05
Diluted (in dollars per share)	$ (5.77)	$ (0.46)	$ (0.35)	$ 0.14	$ 0.42	$ (0.18)	$ 0.26	$ 0.04	$ (6.65)	$ 0.54	$ 1.04