Impairment Charges and Mine Closure Costs (Details) - USD ($) $ in Thousands	3 Months Ended									6 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment and mine closure costs	$ 488,865	$ 2,120,292	$ 19,146	$ 0	$ 17,541	$ 5,060	$ 1,512	$ 0		$ 2,600,000	$ 2,628,303	$ 24,113	$ 220,879
Prepaid royalties											41,990	15,356	1,104
Impairment charge of higher-cost mining complex			5,600
Restructuring charges											5,100
Plant and equipment									$ 142,800		199,107	1,512	$ 36,296
Fair value of assets									$ 71,300
Royalty Agreements [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Prepaid royalties			$ 12,200
Impairment charge					$ 15,400							$ 48,000
APP [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment and mine closure costs											2,200,000
Other Segments [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment and mine closure costs											$ 400,000