Consolidated Statements of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Total Revenue	$ 170,938		$ 200,825		$ 495,133		$ 577,147
COSTS AND EXPENSES
Costs applicable to sales	125,910	[1]	131,805	[1]	351,492	[1]	362,250	[1]
Amortization	41,985		60,097		123,834		166,686
General and administrative	8,515		16,240		31,809		41,492
Exploration	6,587		3,305		15,957		16,920
Litigation settlement	0		0		0		32,046
Pre-development, reclamation, and other	4,244		4,732		20,019		11,896
Total cost and expenses	187,241		216,179		543,111		631,290
OTHER INCOME (EXPENSE), NET
Fair value adjustments, net	16,105		(20,646)		(3,611)		63,905
Impairment of marketable securities	(1,092)		(870)		(4,614)		(18,097)
Interest and other income	(211)		(1,791)		(2,313)		2,484
Interest expense, net of capitalized interest	(11,616)		(9,662)		(36,980)		(30,324)
Total other income and expense	3,186		(32,969)		(47,518)		17,968
Income before income taxes	(13,117)		(48,323)		(95,496)		(36,175)
Income tax benefit (expense)	16,583		2,058		18,650		(32,860)
NET INCOME (LOSS)	3,466		(46,265)		(76,846)		(69,035)
Other Comprehensive Income (Loss), Net of Tax:
Unrealized gain (loss) on marketable securities, net of tax of $686 and $939 for the three and nine months ended September 30, 2014, respectively	(1,086)		301		(1,487)		(10,756)
Reclassification adjustments for impairment of marketable securities, net of tax of $(423) and $(1,786) for the three and nine months ended September 30, 2014, respectively	669		870		2,828		18,097
Reclassification adjustments for realized loss on sale of marketable securities, net of tax of $(140) and $(150) for the three and nine months ended September 30, 2014, respectively	221		136		238		136
Other comprehensive income (loss)	(196)		1,307		1,579		7,477
COMPREHENSIVE INCOME	$ 3,270		$ (44,958)		$ (75,267)		$ (61,558)
BASIC AND DILUTED INCOME PER SHARE
Basic (in dollars per share)	$ 0.03		$ (0.46)		$ (0.75)		$ (0.71)
Diluted (in dollars per share)	$ 0.03		$ (0.46)		$ (0.75)		$ (0.71)

[1] Excludes amortization.