Guarantor Subsidiaries Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Current Assets:
Cash and Cash Equivalents	$ 25,058	$ 21,878	$ 287,313	$ 375,736
Accounts and Notes Receivable:
Trade	408,350	428,328
Notes Receivable, Related Parties, Current	322,406	318,387
Other Receivables	153,697	131,131
Accounts Receivable - Securitized	30,119	37,846
Inventories	217,034	247,766
Recoverable Income Taxes	6,602	0
Deferred Income Taxes	160,750	148,104
Restricted Cash and Cash Equivalents, Current	0	48,294
Prepaid Expenses	115,156	157,360
Total Current Assets	1,439,172	1,539,094
Property, Plant and Equipment:
Property, Plant and Equipment	15,749,523	15,545,204
Less-Accumulated Depreciation, Depletion and Amortization	5,516,319	5,354,237
Total Property, Plant and Equipment-Net	10,233,204	10,190,967
Other Assets:
Deferred Income Taxes	425,079	444,585
Restricted Cash and Cash Equivalents, Noncurrent	20,383	20,379
Investments in Unconsolidated Equity Affiliates	248,127	222,830
Notes, Loans and Financing Receivable, Net	25,995	25,977
Other	201,234	227,077
Total Other Assets	920,818	940,848
Total Assets	12,593,194	12,670,909	12,595,611
Current Liabilities:
Accounts Payable	463,886	507,982
Accounts Payable (Recoverable)- Related Parties	0	0
Short-Term Notes Payable		25,073
Current Portion Long-Term Debt	13,353	13,485
Short-Term Notes Payable	0	25,073
Secured Debt, Current	30,119	37,846
Accrued Income Taxes, Current	0	34,219
Other Accrued Liabilities	839,294	768,494
Total Current Liabilities	1,346,652	1,387,099
Long-Term Debt:	3,172,539	3,174,586
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	2,825,925	2,832,401
Pneumoconiosis	175,952	174,781
Mine Closing	449,891	446,727
Gas Well Closing	150,973	148,928
Workers' Compensation	154,573	155,648
Salary Retirement	172,306	218,004
Reclamation	43,833	47,965
Other	128,316	131,025
Total Deferred Credits and Other Liabilities	4,101,769	4,155,479
Total CONSOL Energy Inc. Stockholders' Equity	3,972,538	3,953,792
Noncontrolling Interest	(304)	(47)
TOTAL LIABILITIES AND EQUITY	12,593,194	12,670,909
Parent Issuer
Current Assets:
Cash and Cash Equivalents	22,152	17,491
Accounts and Notes Receivable:
Trade	0	0
Notes Receivable, Related Parties, Current	194	154
Other Receivables	5,081	6,335
Accounts Receivable - Securitized	0	0
Inventories	0	0
Recoverable Income Taxes	20,580
Deferred Income Taxes	169,920	174,176
Restricted Cash and Cash Equivalents, Current		0
Prepaid Expenses	20,814	29,589
Total Current Assets	238,741	227,745
Property, Plant and Equipment:
Property, Plant and Equipment	218,234	216,448
Less-Accumulated Depreciation, Depletion and Amortization	130,556	126,048
Total Property, Plant and Equipment-Net	87,678	90,400
Other Assets:
Deferred Income Taxes	855,493	884,310
Restricted Cash and Cash Equivalents, Noncurrent	0	0
Investments in Unconsolidated Equity Affiliates	9,992,921	9,917,050
Notes, Loans and Financing Receivable, Net	212	239
Other	115,911	118,938
Total Other Assets	10,964,537	10,920,537
Total Assets	11,290,956	11,238,682
Current Liabilities:
Accounts Payable	195,092	177,734
Accounts Payable (Recoverable)- Related Parties	3,687,347	3,599,216
Short-Term Notes Payable		25,073
Current Portion Long-Term Debt	1,568	1,554
Short-Term Notes Payable	0
Secured Debt, Current	0	0
Accrued Income Taxes, Current		20,488
Other Accrued Liabilities	161,155	135,407
Total Current Liabilities	4,045,162	3,959,472
Long-Term Debt:	3,005,254	3,005,515
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis	0	0
Mine Closing	0	0
Gas Well Closing	0	0
Workers' Compensation	0	0
Salary Retirement	172,306	218,004
Reclamation	0	0
Other	95,696	101,899
Total Deferred Credits and Other Liabilities	268,002	319,903
Total CONSOL Energy Inc. Stockholders' Equity	3,972,538	3,953,792
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	11,290,956	11,238,682
CNX Gas Guarantor
Current Assets:
Cash and Cash Equivalents	2,170	3,352
Accounts and Notes Receivable:
Trade	55,755	58,126
Notes Receivable, Related Parties, Current	319,756	315,730
Other Receivables	112,802	214,748
Accounts Receivable - Securitized	0	0
Inventories	13,979	14,133
Recoverable Income Taxes	(13,978)
Deferred Income Taxes	(9,170)	(26,072)
Restricted Cash and Cash Equivalents, Current		0
Prepaid Expenses	52,271	86,186
Total Current Assets	533,585	666,203
Property, Plant and Equipment:
Property, Plant and Equipment	6,122,433	5,956,207
Less-Accumulated Depreciation, Depletion and Amortization	1,012,595	960,613
Total Property, Plant and Equipment-Net	5,109,838	4,995,594
Other Assets:
Deferred Income Taxes	(430,414)	(439,725)
Restricted Cash and Cash Equivalents, Noncurrent	0	0
Investments in Unconsolidated Equity Affiliates	167,058	143,876
Notes, Loans and Financing Receivable, Net	0	0
Other	46,350	65,935
Total Other Assets	(217,006)	(229,914)
Total Assets	5,426,417	5,431,883
Current Liabilities:
Accounts Payable	173,468	166,182
Accounts Payable (Recoverable)- Related Parties	24,929	23,981
Short-Term Notes Payable		0
Current Portion Long-Term Debt	5,939	5,953
Short-Term Notes Payable	29,000
Secured Debt, Current	0	0
Accrued Income Taxes, Current		13,731
Other Accrued Liabilities	68,331	57,074
Total Current Liabilities	301,667	266,921
Long-Term Debt:	44,671	46,081
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis	0	0
Mine Closing	0	0
Gas Well Closing	81,296	80,097
Workers' Compensation	0	0
Salary Retirement	0	0
Reclamation	0	0
Other	26,151	24,518
Total Deferred Credits and Other Liabilities	107,447	104,615
Total CONSOL Energy Inc. Stockholders' Equity	4,972,936	5,014,313
Noncontrolling Interest	(304)	(47)
TOTAL LIABILITIES AND EQUITY	5,426,417	5,431,883
Other Guarantors Subsidiaries [Member]
Current Assets:
Cash and Cash Equivalents	171	175
Accounts and Notes Receivable:
Trade	0	0
Notes Receivable, Related Parties, Current	2,456	2,503
Other Receivables	32,024	33,289
Accounts Receivable - Securitized	0	0
Inventories	167,935	198,269
Recoverable Income Taxes	0
Deferred Income Taxes	0	0
Restricted Cash and Cash Equivalents, Current		48,294
Prepaid Expenses	40,544	40,215
Total Current Assets	243,130	322,745
Property, Plant and Equipment:
Property, Plant and Equipment	9,383,357	9,347,370
Less-Accumulated Depreciation, Depletion and Amortization	4,354,755	4,249,507
Total Property, Plant and Equipment-Net	5,028,602	5,097,863
Other Assets:
Deferred Income Taxes	0	0
Restricted Cash and Cash Equivalents, Noncurrent	20,383	20,379
Investments in Unconsolidated Equity Affiliates	798,589	769,058
Notes, Loans and Financing Receivable, Net	25,783	25,738
Other	28,940	32,016
Total Other Assets	873,695	847,191
Total Assets	6,145,427	6,267,799
Current Liabilities:
Accounts Payable	85,104	154,936
Accounts Payable (Recoverable)- Related Parties	(3,969,054)	(3,749,584)
Short-Term Notes Payable		0
Current Portion Long-Term Debt	5,084	5,222
Short-Term Notes Payable	0
Secured Debt, Current	0	0
Accrued Income Taxes, Current		0
Other Accrued Liabilities	599,867	566,485
Total Current Liabilities	(3,278,999)	(3,022,941)
Long-Term Debt:	121,151	121,523
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	2,825,925	2,832,401
Pneumoconiosis	175,952	174,781
Mine Closing	449,891	446,727
Gas Well Closing	69,677	68,831
Workers' Compensation	154,261	155,342
Salary Retirement	0	0
Reclamation	43,833	47,965
Other	6,469	4,608
Total Deferred Credits and Other Liabilities	3,726,008	3,730,655
Total CONSOL Energy Inc. Stockholders' Equity	5,577,267	5,438,562
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	6,145,427	6,267,799
Non-Guarantors
Current Assets:
Cash and Cash Equivalents	565	860
Accounts and Notes Receivable:
Trade	352,595	370,202
Notes Receivable, Related Parties, Current	0	0
Other Receivables	3,790	5,159
Accounts Receivable - Securitized	30,119	37,846
Inventories	35,120	35,364
Recoverable Income Taxes	0
Deferred Income Taxes	0	0
Restricted Cash and Cash Equivalents, Current		0
Prepaid Expenses	1,527	1,370
Total Current Assets	423,716	450,801
Property, Plant and Equipment:
Property, Plant and Equipment	25,499	25,179
Less-Accumulated Depreciation, Depletion and Amortization	18,413	18,069
Total Property, Plant and Equipment-Net	7,086	7,110
Other Assets:
Deferred Income Taxes	0	0
Restricted Cash and Cash Equivalents, Noncurrent	0	0
Investments in Unconsolidated Equity Affiliates	0	0
Notes, Loans and Financing Receivable, Net	0	0
Other	10,033	10,188
Total Other Assets	10,033	10,188
Total Assets	440,835	468,099
Current Liabilities:
Accounts Payable	10,222	9,130
Accounts Payable (Recoverable)- Related Parties	227,778	254,787
Short-Term Notes Payable		0
Current Portion Long-Term Debt	762	756
Short-Term Notes Payable	0
Secured Debt, Current	30,119	37,846
Accrued Income Taxes, Current		0
Other Accrued Liabilities	9,941	9,528
Total Current Liabilities	278,822	312,047
Long-Term Debt:	1,463	1,467
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis	0	0
Mine Closing	0	0
Gas Well Closing	0	0
Workers' Compensation	312	306
Salary Retirement	0	0
Reclamation	0	0
Other	0	0
Total Deferred Credits and Other Liabilities	312	306
Total CONSOL Energy Inc. Stockholders' Equity	160,238	154,279
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	440,835	468,099
Consolidation, Eliminations [Member]
Current Assets:
Cash and Cash Equivalents	0	0
Accounts and Notes Receivable:
Trade	0	0
Notes Receivable, Related Parties, Current	0	0
Other Receivables	0	(128,400)
Accounts Receivable - Securitized	0	0
Inventories	0	0
Recoverable Income Taxes	0
Deferred Income Taxes	0	0
Restricted Cash and Cash Equivalents, Current		0
Prepaid Expenses	0	0
Total Current Assets	0	(128,400)
Property, Plant and Equipment:
Property, Plant and Equipment	0	0
Less-Accumulated Depreciation, Depletion and Amortization	0	0
Total Property, Plant and Equipment-Net	0	0
Other Assets:
Deferred Income Taxes	0	0
Restricted Cash and Cash Equivalents, Noncurrent	0	0
Investments in Unconsolidated Equity Affiliates	(10,710,441)	(10,607,154)
Notes, Loans and Financing Receivable, Net	0	0
Other	0	0
Total Other Assets	(10,710,441)	(10,607,154)
Total Assets	(10,710,441)	(10,735,554)
Current Liabilities:
Accounts Payable	0	0
Accounts Payable (Recoverable)- Related Parties	29,000	(128,400)
Short-Term Notes Payable		0
Current Portion Long-Term Debt	0	0
Short-Term Notes Payable	(29,000)
Secured Debt, Current	0	0
Accrued Income Taxes, Current		0
Other Accrued Liabilities	0	0
Total Current Liabilities	0	(128,400)
Long-Term Debt:	0	0
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis	0	0
Mine Closing	0	0
Gas Well Closing	0	0
Workers' Compensation	0	0
Salary Retirement	0	0
Reclamation	0	0
Other	0	0
Total Deferred Credits and Other Liabilities	0	0
Total CONSOL Energy Inc. Stockholders' Equity	(10,710,441)	(10,607,154)
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	$ (10,710,441)	$ (10,735,554)