Significant Accounting Policy Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income Attributable to CONSOL Energy Inc Shareholders	$ 195,635	$ 167,329	$ 77,384	$ 192,149	$ 104,461	$ 75,383	$ 66,668	$ 100,269	$ 632,497	$ 346,781	$ 539,717
Weighted Average Number of Shares Outstanding, Basic	226,971,597	226,744,011	226,647,752	226,350,594	225,854,413	225,781,539	225,715,539	181,726,480	226,680,369	214,920,561	180,693,243
Effect of stock-based compensation awards									2,323,230	2,117,243	2,127,893
Weighted Average Number of Shares Outstanding, Diluted	229,314,370	229,163,537	229,138,024	228,814,838	228,169,569	228,092,299	228,081,103	184,348,982	229,003,599	217,037,804	182,821,136
Earnings Per Share, Basic	$ 0.86	$ 0.74	$ 0.34	$ 0.85	$ 0.46	$ 0.33	$ 0.30	$ 0.55	$ 2.79	$ 1.61	$ 2.99
Earnings Per Share, Diluted	$ 0.85	$ 0.73	$ 0.34	$ 0.84	$ 0.46	$ 0.33	$ 0.29	$ 0.54	$ 2.76	$ 1.60	$ 2.95