CONSOLIDATED STATEMENTS OF CASH FLOWS (Cloud Peak Energy Inc. and Subsidiaries) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities
Net income	$ 189,797	$ 117,197	$ 393,550
Income or loss from discontinued operations, net of tax			(211,078)
Depreciation and depletion	87,127	100,023	97,869
Amortization		3,197	28,719
Accretion	12,469	12,499	12,587
Asset impairment charges		659	698
Earnings from unconsolidated affiliates	(1,801)	(3,189)	(1,381)
Distributions of income from equity investments	5,250	35	4,000
Deferred income taxes	(11,224)	28,503	13,595
Tax agreement expense	19,854	19,669
Stock compensation expense	8,796	7,234	1,919
Marked-to-market adjustments	(2,275)
Other, net	11,506	4,718	750
Changes in operating assets and liabilities:
Accounts receivable, net	(30,074)	17,636	(3,358)
Inventories	(6,452)	(638)	(7,638)
Due to or from related parties	(37)	7,906	103,414
Other assets	4,436	(10,090)	(1,097)
Accounts payable and accrued expenses	26,327	27,040	28,890
Tax agreement liability	(9,409)	(1,685)
Asset retirement obligations	(7,506)	(5,938)	(4,855)
Net cash provided by operating activities from continuing operations	296,784	324,776	456,584
Investing activities
Purchases of property, plant and equipment	(142,722)	(91,639)	(119,742)
Investments in marketable securities	(75,228)
Initial payment on federal coal leases	(69,407)
Return of restricted cash	110,972	116,533
Restricted cash deposit		(218,425)	(80,180)
Change in cash advances to affiliate			(217,468)
Other	713	1,511	313
Net cash used in investing activities from continuing operations	(175,672)	(192,020)	(417,077)
Financing activities
Borrowings on long term debt			595,284
Principal payments on federal coal leases	(54,630)	(50,768)	(68,583)
Payment of debt issue costs			(26,585)
Proceeds from issuance of common stock			433,755
Distributions to former parent		(10,203)	(1,516,058)
Other	(2,343)
Net cash used in financing activities from continuing operations	(56,973)	(60,971)	(582,187)
Net cash provided by (used in) continuing operations	64,139	71,785	(542,680)
Cash flows from discontinued operations
Net cash from operating activities			36,029
Net cash from investing activities			759,032
Net cash provided by discontinued operations			795,061
Net increase in cash and cash equivalents	64,139	71,785	252,381
Cash and cash equivalents at beginning of period	340,101	268,316	15,935
Cash and cash equivalents at end of period	404,240	340,101	268,316
Supplemental cash flow disclosures for continuing operations:
Interest paid	62,792	69,317	17,606
Income taxes paid, net	6,161	9,120	79,089
Supplemental noncash investing and financing activities from continuing operations:
Obligations to acquire federal coal leases and other mineral rights	224,658		37,424
Noncash capital contributions from former parent			$ 158,400