Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue		$ 214,858	$ 154,249	$ 416,975	$ 327,416
COSTS AND EXPENSES
Amortization		31,973	27,876	61,910	64,038
General and administrative		10,467	8,616	22,021	17,536
Pre-development, reclamation, and other		12,738	18,675	26,450	25,230
Total costs and expenses		200,219	157,037	373,235	333,977
OTHER INCOME (EXPENSE), NET
Loss on debt extinguishments		0	0	(9,173)	0
Fair value adjustments, net, pretax		37,239	10,067	33,440	1,248
Interest expense, net of capitalized interest		(5,093)	(5,765)	(10,003)	(10,893)
Other, net		701	121	4,328	2,002
Total other income (expense), net		32,847	4,423	18,592	(7,643)
Total		47,486	1,635	62,332	(14,204)
Income and mining tax (expense) benefit		(15,340)	(2,844)	(28,126)	1,095
NET INCOME (LOSS)		32,146	(1,209)	34,206	(13,109)
OTHER COMPREHENSIVE INCOME (LOSS), Net of Tax:
Unrealized gain (loss) on hedger, net of tax		(2,982)	(7,097)	24,376	(6,891)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		(3,061)	(679)	(5,783)	(679)
Other comprehensive income (loss)		(6,043)	(7,776)	18,593	(7,570)
COMPREHENSIVE INCOME (LOSS)		$ 26,103	$ (8,985)	$ 52,799	$ (20,679)
Basic EPS
Earnings Per Share, Basic		$ 0.13	$ (0.01)	$ 0.14	$ (0.05)
Diluted EPS
Earnings Per Share, Diluted		$ 0.13	$ (0.01)	$ 0.14	$ (0.05)
Accumulated Deficit [Member]
OTHER INCOME (EXPENSE), NET
NET INCOME (LOSS)		$ 32,146	$ (1,209)
Product
COSTS AND EXPENSES
Costs applicable to sales	[1]	132,595	90,015	$ 240,742	$ 208,932
Mineral, Exploration
COSTS AND EXPENSES
Costs applicable to sales		$ 12,446	$ 11,855	$ 22,112	$ 18,241

[1] Excludes amortization.