Significant Accounting Policy Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income (Loss) from Continuing Operations Attributable to Parent	$ 73,666	$ (1,645)	$ 146,595	$ (24,935)	$ 121,691	$ (72,169)	$ 8,562	$ (3,724)	$ 168,777	$ 79,264	$ 317,959
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	0	0	591,144	0	(5,687)	8,120	(21,375)	1,903	(5,687)	579,792	70,114
Less: Net Loss (Income) Attributable to Noncontrolling Interest									0	1,386	397
Net Income Attributable to CONSOL Energy Inc Shareholders	$ 73,666us-gaap_NetIncomeLoss	$ (1,645)us-gaap_NetIncomeLoss	$ 738,183us-gaap_NetIncomeLoss	$ (24,935)us-gaap_NetIncomeLoss	$ 116,004us-gaap_NetIncomeLoss	$ (63,651)us-gaap_NetIncomeLoss	$ (12,526)us-gaap_NetIncomeLoss	$ (1,564)us-gaap_NetIncomeLoss	$ 163,090us-gaap_NetIncomeLoss	$ 660,442us-gaap_NetIncomeLoss	$ 388,470us-gaap_NetIncomeLoss
Weighted Average Number of Shares Outstanding, Basic									229,994,407	228,728,628	227,593,524
Effect of stock-based compensation awards									1,585,871	1,349,314	1,548,243
Weighted Average Number of Shares Outstanding, Diluted									231,580,278	230,077,942	229,141,767
Earnings Per Share, Basic	$ 0.32us-gaap_EarningsPerShareBasic	$ (0.01)us-gaap_EarningsPerShareBasic	$ 3.23us-gaap_EarningsPerShareBasic	$ (0.11)us-gaap_EarningsPerShareBasic	$ 0.51us-gaap_EarningsPerShareBasic	$ (0.28)us-gaap_EarningsPerShareBasic	$ (0.05)us-gaap_EarningsPerShareBasic	$ (0.01)us-gaap_EarningsPerShareBasic	$ 0.71us-gaap_EarningsPerShareBasic	$ 2.89us-gaap_EarningsPerShareBasic	$ 1.71us-gaap_EarningsPerShareBasic
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	$ 0.00	$ 0.00	$ 2.59	$ 0.00	$ (0.02)	$ 0.03	$ (0.09)	$ 0.01	$ (0.02)	$ 2.54	$ 0.31
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.32	$ (0.01)	$ 0.64	$ (0.11)	$ 0.53	$ (0.31)	$ 0.04	$ (0.02)	$ 0.73	$ 0.35	$ 1.40
Earnings Per Share, Diluted	$ 0.32us-gaap_EarningsPerShareDiluted	$ (0.01)us-gaap_EarningsPerShareDiluted	$ 3.21us-gaap_EarningsPerShareDiluted	$ (0.11)us-gaap_EarningsPerShareDiluted	$ 0.50us-gaap_EarningsPerShareDiluted	$ (0.28)us-gaap_EarningsPerShareDiluted	$ (0.05)us-gaap_EarningsPerShareDiluted	$ (0.01)us-gaap_EarningsPerShareDiluted	$ 0.70us-gaap_EarningsPerShareDiluted	$ 2.87us-gaap_EarningsPerShareDiluted	$ 1.70us-gaap_EarningsPerShareDiluted
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.00	$ 0.00	$ 2.57	$ 0.00	$ (0.03)	$ 0.03	$ (0.09)	$ 0.01	$ (0.03)	$ 2.52	$ 0.31
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.32	$ (0.01)	$ 0.64	$ (0.11)	$ 0.53	$ (0.31)	$ 0.04	$ (0.02)	$ 0.73	$ 0.35	$ 1.39

After tax income (loss) from operations of a business component (exclusive of any gain (loss) on disposal, or provision therefore) during the reporting period, until its disposal.

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