CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Cloud Peak Energy Inc. and Subsidiaries) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenues	$ 406,950	$ 372,364	$ 1,151,174	$ 1,024,960
Costs and expenses
Cost of product sold (exclusive of depreciation, depletion, amortization and accretion, shown separately)	306,533	262,166	855,551	719,007
Depreciation and depletion	24,289	25,997	58,537	75,212
Amortization				3,197
Accretion	2,984	3,337	9,420	9,903
Selling, general and administrative expenses	12,971	16,514	38,905	47,159
Total costs and expenses	346,777	308,014	962,413	854,478
Operating income	60,173	64,350	188,761	170,482
Other income (expense)
Interest income	143	184	459	411
Interest expense	(6,848)	(11,404)	(27,520)	(36,186)
Tax agreement (expense) benefit	22,878	(19,669)	(19,855)	(19,669)
Other, net	(103)	84	(34)	123
Total other income (expense)	16,070	(30,805)	(46,950)	(55,321)
Income before income tax provision and earnings from unconsolidated affiliates	76,243	33,545	141,811	115,161
Income tax (expense) benefit	(52,162)	(14,712)	2,025	(30,212)
Earnings from unconsolidated affiliates, net of tax	530	683	2,142	2,499
Net income	24,611	19,516	145,978	87,448
Less: Net income attributable to noncontrolling interest		26,115		66,592
Net income (loss) attributable to controlling interest	$ 24,611	$ (6,599)	$ 145,978	$ 20,856
Earnings (loss) per common share attributable to controlling interest:
Basic (in dollars per share)	$ 0.41	$ (0.22)	$ 2.43	$ 0.68
Diluted (in dollars per share)	$ 0.41	$ (0.22)	$ 2.41	$ 0.68
Weighted-average shares outstanding - basic (in shares)	60,007	30,600	60,003	30,600
Weighted-average shares outstanding - diluted (in shares)	60,645	30,600	60,606	30,600