Significant Accounting Policy Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income (Loss) from Continuing Operations Attributable to Parent	$ 34,325	$ 125,470	$ 73,666	$ (603,301)	$ 79,031	$ (1,645)	$ (24,935)	$ 121,691	$ (364,475)	$ 168,777	$ 79,264
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	0	0	0	0	0	0	0	(5,687)	0	(5,687)	579,792
Less: Net Loss (Income) Attributable to Noncontrolling Interest									(10,410)	0	1,386
Net Income Attributable to CONSOL Energy Inc Shareholders	$ 30,405	$ 118,980	$ 73,666	$ (603,301)	$ 79,031	$ (1,645)	$ (24,935)	$ 116,004	$ (374,885)	$ 163,090	$ 660,442
Weighted Average Number of Shares Outstanding, Basic									229,186,125	229,994,407	228,728,628
Effect of stock-based compensation awards									0	1,585,871	1,349,314
Weighted Average Number of Shares Outstanding, Diluted									229,186,125	231,580,278	230,077,942
Earnings Per Share, Basic	$ 0.13	$ 0.52	$ 0.32	$ (2.64)	$ 0.34	$ (0.01)	$ (0.11)	$ 0.51	$ (1.64)	$ 0.71	$ 2.89
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.00	0.00	0.00	0.00	0.00	0.00	0.00	(0.02)	0.00	(0.02)	2.54
Income (Loss) from Continuing Operations, Per Basic Share	0.13	0.52	0.32	(2.64)	0.34	(0.01)	(0.11)	0.53	(1.64)	0.73	0.35
Earnings Per Share, Diluted	0.13	0.52	0.32	(2.64)	0.34	(0.01)	(0.11)	0.50	(1.64)	0.70	2.87
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0.00	0.00	0.00	0.00	0.00	0.00	0.00	(0.03)	0.00	(0.03)	2.52
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.13	$ 0.52	$ 0.32	$ (2.64)	$ 0.34	$ (0.01)	$ (0.11)	$ 0.53	$ (1.64)	$ 0.73	$ 0.35