CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Cloud Peak Energy Inc. and Subsidiaries) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2010
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME
Revenue	$ 1,370,761
Costs and expenses
Cost of product sold (exclusive of depreciation, depletion, amortization and accretion, shown separately)	979,573
Depreciation and depletion	100,023
Amortization	3,197
Accretion	12,499
Selling, general and administrative expenses	63,594
Total costs and expenses	1,158,886
Operating income	211,875
Other income (expense)
Interest income	565
Interest expense	(46,938)
Tax agreement benefit (expense)	(19,669)
Other, net	157
Total other expense	(65,885)
Income before income tax provision and earnings from unconsolidated affiliates	145,990
Income tax expense	(31,982)
Earnings from unconsolidated affiliates, net of tax	3,189
Net income	117,197
Less: Net income attributable to noncontrolling interest	83,460
Net income attributable to controlling interest	33,737
Other comprehensive income
Retiree medical plan amortization of prior service costs	1,405
Retiree medical plan adjustment	(3,587)
Decker pension adjustments	295
Income tax on retiree medical plan and pension adjustments	916
Other comprehensive income	(971)
Total comprehensive income	116,226
Less: Comprehensive income attributable to the noncontrolling interest	(84,114)
Total comprehensive income attributable to controlling interest	$ 32,112
Earnings per common share attributable to controlling interest:
Basic (in dollars per share)	$ 1.06
Diluted (in dollars per share)	$ 1.06
Weighted-average shares outstanding - basic (in shares)	31,889
Weighted-average shares outstanding - diluted (in shares)	31,889