Guarantor Subsidiaries Balance Sheet (Detail) (USD $)	Dec. 31, 2011	Jan. 02, 2011	Dec. 31, 2010	Dec. 31, 2009	Jan. 02, 2009	Dec. 31, 2008
Current Assets:
Cash and Cash Equivalents	$ 375,736,000	$ 32,794,000	$ 32,794,000	$ 65,607,000	$ 65,607,000	$ 138,512,000
Accounts and Notes Receivable:
Trade	462,812,000		252,530,000
Securitized	0		200,000,000
Notes, Loans and Financing Receivable, Net, Current	314,950,000		408,000
Other Receivables	105,708,000		21,181,000
Inventories	258,335,000		258,538,000
Recoverable income taxes	0		32,528,000
Deferred Income Taxes	141,083,000		174,171,000
Prepaid Expenses	239,353,000		142,856,000
Total Current Assets	1,897,977,000		1,115,006,000
Property, Plant and Equipment:
Property, Plant and Equipment, Gross	14,087,319,000		14,951,358,000
Less-Accumulated Depreciation, Depletion and Amortization	4,760,903,000		4,822,107,000
Total Property, Plant and Equipment-Net	9,326,416,000		10,129,251,000	6,124,290,000
Other Assets:
Deferred Income Taxes	507,724,000		484,846,000
Investments in Unconsolidated Equity Affiliates	182,036,000		93,509,000
Restricted Cash	22,148,000		20,291,000
Notes, Loans and Financing Receivable, Net, Noncurrent	300,492,000		6,866,000
Other	288,907,000		220,841,000
Total Other Assets	1,301,307,000		826,353,000
Total Assets	12,525,700,000		12,070,610,000	7,775,401,000
Current Liabilities:
Accounts Payable	522,003,000		354,011,000
Accounts Payable (Recoverable)- Related Parties	0		0
Short-Term Notes Payable			284,000,000
Current Portion Long-Term Debt	20,691,000		24,783,000
Accrued Income Taxes	75,633,000
Accrued Liabilities, Current	770,070,000		801,991,000
Borrowings under Securitization Facility	0		200,000,000
Other Accrued Liabilities, Current	128,247,000		139,079,000
Total Current Liabilities	1,388,397,000		1,664,785,000
Long-Term Debt:	3,177,423,000		3,186,138,000
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	3,059,671,000		3,077,390,000
Pneumoconiosis	173,553,000		173,616,000
Mine Closing	406,712,000		393,754,000
Gas Well Closing	124,051,000		130,978,000
Workers' Compensation	151,034,000		148,314,000
Salary Retirement	269,069,000		161,173,000
Reclamation	39,969,000		53,839,000
Other	124,936,000		144,610,000
Total Deferred Credits and Other Liabilities	4,348,995,000		4,283,674,000
Total CONSOL Energy Inc. Stockholders' Equity	3,610,885,000		2,944,477,000
Noncontrolling Interest	0		(8,464,000)
TOTAL LIABILITIES AND EQUITY	12,525,700,000		12,070,610,000
Parent Issuer
Current Assets:
Cash and Cash Equivalents	37,342,000		11,382,000
Accounts and Notes Receivable:
Trade	0		0
Securitized	0		200,000,000
Notes, Loans and Financing Receivable, Net, Current	2,669,000		408,000
Other Receivables	2,913,000		4,227,000
Inventories	0		0
Recoverable income taxes			(3,189,000)
Deferred Income Taxes	191,689,000		173,211,000
Prepaid Expenses	28,470,000		35,297,000
Total Current Assets	263,083,000		421,336,000
Property, Plant and Equipment:
Property, Plant and Equipment, Gross	198,004,000		166,884,000
Less-Accumulated Depreciation, Depletion and Amortization	109,924,000		91,952,000
Total Property, Plant and Equipment-Net	88,080,000		74,932,000
Other Assets:
Deferred Income Taxes	963,332,000		902,188,000
Investments in Unconsolidated Equity Affiliates	9,126,453,000		7,833,948,000
Restricted Cash	22,148,000		20,291,000
Notes, Loans and Financing Receivable, Net, Noncurrent	4,148,000		6,866,000
Other	116,624,000		111,283,000
Total Other Assets	10,232,705,000		8,874,576,000
Total Assets	10,583,868,000		9,370,844,000
Current Liabilities:
Accounts Payable	140,823,000		130,063,000
Accounts Payable (Recoverable)- Related Parties	2,900,546,000		2,363,108,000
Short-Term Notes Payable			155,000,000
Current Portion Long-Term Debt	805,000		758,000
Accrued Income Taxes	68,819,000
Accrued Liabilities, Current	493,450,000		302,788,000
Borrowings under Securitization Facility			200,000,000
Total Current Liabilities	3,604,443,000		3,151,717,000
Long-Term Debt:	3,001,092,000		3,000,702,000
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	269,069,000		161,173,000
Reclamation	0		0
Other	98,379,000		112,775,000
Total Deferred Credits and Other Liabilities	367,448,000		273,948,000
Total CONSOL Energy Inc. Stockholders' Equity	3,610,885,000		2,944,477,000
Noncontrolling Interest	0		0
TOTAL LIABILITIES AND EQUITY	10,583,868,000		9,370,844,000
Cnx Gas Guarantor [Member]
Current Assets:
Cash and Cash Equivalents	336,727,000		16,559,000
Accounts and Notes Receivable:
Trade	63,299,000		65,197,000
Securitized	0		0
Notes, Loans and Financing Receivable, Net, Current	311,754,000		0
Other Receivables	91,582,000		3,361,000
Inventories	8,600,000		4,456,000
Recoverable income taxes			35,717,000
Deferred Income Taxes	(50,606,000)		960,000
Prepaid Expenses	159,900,000		57,907,000
Total Current Assets	921,256,000		184,157,000
Property, Plant and Equipment:
Property, Plant and Equipment, Gross	5,488,094,000		6,336,121,000
Less-Accumulated Depreciation, Depletion and Amortization	778,716,000		628,506,000
Total Property, Plant and Equipment-Net	4,709,378,000		5,707,615,000
Other Assets:
Deferred Income Taxes	(455,608,000)		(417,342,000)
Investments in Unconsolidated Equity Affiliates	96,914,000		23,569,000
Restricted Cash	0		0
Notes, Loans and Financing Receivable, Net, Noncurrent	296,344,000		0
Other	110,128,000		37,268,000
Total Other Assets	47,778,000		(356,505,000)
Total Assets	5,678,412,000		5,535,267,000
Current Liabilities:
Accounts Payable	206,072,000		101,944,000
Accounts Payable (Recoverable)- Related Parties	9,431,000		30,302,000
Short-Term Notes Payable			129,000,000
Current Portion Long-Term Debt	5,587,000		9,851,000
Accrued Income Taxes	6,814,000
Accrued Liabilities, Current	58,401,000		59,960,000
Borrowings under Securitization Facility			0
Total Current Liabilities	286,305,000		331,057,000
Long-Term Debt:	50,326,000		58,905,000
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	0		0
Pneumoconiosis	0		0
Mine Closing	0		0
Gas Well Closing	61,954,000		60,027,000
Workers' Compensation	0		0
Salary Retirement	0		0
Reclamation	0		0
Other	16,899,000		25,483,000
Total Deferred Credits and Other Liabilities	78,853,000		85,510,000
Total CONSOL Energy Inc. Stockholders' Equity	5,262,928,000		5,068,259,000
Noncontrolling Interest	0		(8,464,000)
TOTAL LIABILITIES AND EQUITY	5,678,412,000		5,535,267,000
Other Subsidiary Guarantors
Current Assets:
Cash and Cash Equivalents	1,269,000		3,235,000
Accounts and Notes Receivable:
Trade	(5,081,000)		646,000
Securitized	0		0
Notes, Loans and Financing Receivable, Net, Current	527,000		0
Other Receivables	7,458,000		10,915,000
Inventories	206,096,000		203,962,000
Recoverable income taxes			0
Deferred Income Taxes	0		0
Prepaid Expenses	49,224,000		39,309,000
Total Current Assets	259,493,000		258,067,000
Property, Plant and Equipment:
Property, Plant and Equipment, Gross	8,376,831,000		8,422,235,000
Less-Accumulated Depreciation, Depletion and Amortization	3,855,323,000		4,083,693,000
Total Property, Plant and Equipment-Net	4,521,508,000		4,338,542,000
Other Assets:
Deferred Income Taxes	0		0
Investments in Unconsolidated Equity Affiliates	760,548,000		952,138,000
Restricted Cash	0		0
Notes, Loans and Financing Receivable, Net, Noncurrent	0		0
Other	52,009,000		61,532,000
Total Other Assets	812,557,000		1,013,670,000
Total Assets	5,593,558,000		5,610,279,000
Current Liabilities:
Accounts Payable	164,521,000		113,036,000
Accounts Payable (Recoverable)- Related Parties	(3,228,229,000)		(2,543,991,000)
Short-Term Notes Payable			0
Current Portion Long-Term Debt	13,543,000		13,589,000
Accrued Income Taxes	0
Accrued Liabilities, Current	206,649,000		425,735,000
Borrowings under Securitization Facility			0
Total Current Liabilities	(2,843,516,000)		(1,991,631,000)
Long-Term Debt:	124,674,000		125,627,000
Deferred Credits and Other Liabilities
Postretirement Benefits Other Than Pensions	3,059,671,000		3,077,390,000
Pneumoconiosis	173,553,000		173,616,000
Mine Closing	406,712,000		393,754,000
Gas Well Closing	62,097,000		70,951,000
Workers' Compensation	150,786,000		148,265,000
Salary Retirement	0		0
Reclamation	39,969,000		53,839,000
Other	9,658,000		6,352,000
Total Deferred Credits and Other Liabilities	3,902,446,000		3,924,167,000
Total CONSOL Energy Inc. Stockholders' Equity	4,409,954,000		3,543,652,000
Noncontrolling Interest	0		8,464,000
TOTAL LIABILITIES AND EQUITY	5,593,558,000		5,610,279,000
Non-Guarantors
Current Assets:
Cash and Cash Equivalents	398,000		1,618,000
Accounts and Notes Receivable:
Trade	404,594,000		186,687,000
Securitized	0		0
Notes, Loans and Financing Receivable, Net, Current	0		0
Other Receivables	3,755,000		2,678,000
Inventories	43,639,000		50,120,000
Recoverable income taxes			0
Deferred Income Taxes	0		0
Prepaid Expenses	1,759,000		10,343,000
Total Current Assets	454,145,000		251,446,000
Property, Plant and Equipment:
Property, Plant and Equipment, Gross	24,390,000		26,118,000
Less-Accumulated Depreciation, Depletion and Amortization	16,940,000		17,956,000
Total Property, Plant and Equipment-Net	7,450,000		8,162,000
Other Assets:
Deferred Income Taxes	0		0
Investments in Unconsolidated Equity Affiliates	0		11,087,000
Restricted Cash	0		0
Notes, Loans and Financing Receivable, Net, Noncurrent	0		0
Other	10,146,000		10,758,000
Total Other Assets	10,146,000		21,845,000
Total Assets	471,741,000		281,453,000
Current Liabilities:
Accounts Payable	10,587,000		8,968,000
Accounts Payable (Recoverable)- Related Parties	318,252,000		150,581,000
Short-Term Notes Payable			0
Current Portion Long-Term Debt	756,000		585,000
Accrued Income Taxes	0
Accrued Liabilities, Current	11,570,000		13,508,000
Borrowings under Securitization Facility			0
Total Current Liabilities	341,165,000		173,642,000
Long-Term Debt:	1,331,000		904,000
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	248,000		49,000
Salary Retirement	0		0
Reclamation	0		0
Other	0		0
Total Deferred Credits and Other Liabilities	248,000		49,000
Total CONSOL Energy Inc. Stockholders' Equity	128,997,000		106,858,000
Noncontrolling Interest	0		0
TOTAL LIABILITIES AND EQUITY	471,741,000		281,453,000
Elimination
Current Assets:
Cash and Cash Equivalents	0		0
Accounts and Notes Receivable:
Trade	0		0
Securitized	0		0
Notes, Loans and Financing Receivable, Net, Current	0		0
Other Receivables	0		0
Inventories	0		0
Recoverable income taxes			0
Deferred Income Taxes	0		0
Prepaid Expenses	0		0
Total Current Assets	0		0
Property, Plant and Equipment:
Property, Plant and Equipment, Gross	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
Investments in Unconsolidated Equity Affiliates	(9,801,879,000)		(8,727,233,000)
Restricted Cash	0		0
Notes, Loans and Financing Receivable, Net, Noncurrent	0		0
Other	0		0
Total Other Assets	(9,801,879,000)		(8,727,233,000)
Total Assets	(9,801,879,000)		(8,727,233,000)
Current Liabilities:
Accounts Payable	0		0
Accounts Payable (Recoverable)- Related Parties	0		0
Short-Term Notes Payable			0
Current Portion Long-Term Debt	0		0
Accrued Income Taxes	0
Accrued Liabilities, Current	0		0
Borrowings under Securitization Facility			0
Total Current Liabilities	0		0
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	(9,801,879,000)		(8,718,769,000)
Noncontrolling Interest	0		(8,464,000)
TOTAL LIABILITIES AND EQUITY	$ (9,801,879,000)		$ (8,727,233,000)