CONSOLIDATED BALANCE SHEETS (Cloud Peak Energy Resources LLC and Subsidiaries) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets
Cash and cash equivalents	$ 197,691	$ 404,240
Investments in marketable securities	80,341	75,228
Restricted cash		71,245
Accounts receivable	76,117	95,247
Inventories, net	81,675	71,648
Deferred income taxes	28,112	37,528
Derivative financial instruments	16,107	2,275
Other assets	16,513	13,019
Total current assets	495,795	770,901
Noncurrent assets
Property, plant and equipment, net	1,678,294	1,350,135
Goodwill	35,634	35,634
Deferred income taxes	101,075	132,828
Other assets	40,525	29,821
Total assets	2,351,323	2,319,319
Current liabilities
Accounts payable	49,589	71,427
Royalties and production taxes	129,351	136,072
Accrued expenses	50,364	65,928
Due to related parties		27,420
Current portion of federal coal lease obligations	63,191	102,198
Other liabilities	2,770	4,971
Total current liabilities	314,750	399,709
Noncurrent liabilities
Senior notes	596,506	596,077
Federal coal lease obligations, net of current portion	122,928	186,119
Asset retirement obligations, net of current portion	238,991	192,707
Other liabilities	50,073	42,795
Total liabilities	1,420,301	1,568,930
Commitments and Contingencies (Note 15)
Equity
Accumulated other comprehensive loss	(20,461)	(18,614)
Total equity	931,022	750,389
Total liabilities and equity	2,351,323	2,319,319
CLOUD PEAK ENERGY RESOURCES LLC AND SUBSIDIARIES
Current assets
Cash and cash equivalents	197,691	404,240
Investments in marketable securities	80,341	75,228
Restricted cash		71,245
Accounts receivable	76,117	95,247
Inventories, net	81,675	71,648
Deferred income taxes	21,096	30,648
Derivative financial instruments	13,785	2,275
Other assets	16,224	12,610
Total current assets	486,929	763,141
Noncurrent assets
Property, plant and equipment, net	1,678,294	1,350,135
Goodwill	35,634	35,634
Deferred income taxes	66,136	78,280
Other assets	40,478	29,773
Total assets	2,307,471	2,256,963
Current liabilities
Accounts payable	49,571	71,377
Royalties and production taxes	129,351	136,072
Accrued expenses	43,908	51,799
Due to related parties	10,993	27,420
Current portion of federal coal lease obligations	63,191	102,198
Other liabilities	2,769	4,971
Total current liabilities	299,783	393,837
Noncurrent liabilities
Senior notes	596,506	596,077
Federal coal lease obligations, net of current portion	122,928	186,119
Asset retirement obligations, net of current portion	238,991	192,707
Other liabilities	50,073	42,795
Total liabilities	1,308,281	1,411,535
Commitments and Contingencies (Note 15)
Equity
Member's equity	1,019,651	864,042
Accumulated other comprehensive loss	(20,461)	(18,614)
Total equity	999,190	845,428
Total liabilities and equity	$ 2,307,471	$ 2,256,963