2.4.0.81020 - Disclosure - Accounting Policies and Standards Updatetruefalsefalse1false falsefalseD2013Q2YTDhttp://www.sec.gov/CIK0001441849duration2013-01-01T00:00:002013-06-30T00:00:001true 1us-gaap_AccountingPoliciesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Accounting Policies and Standards Update2false 2us-gaap_SignificantAccountingPoliciesTextBlockus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00<div style="font-size:10.0pt;font-family:Times New Roman;"> 2.  Accounting Policies and Standards Update   Recently Issued Accounting Pronouncements   From time to time, the Financial Accounting Standards Board (“FASB”) or other standard setting bodies issue new accounting pronouncements.  Updates to the FASB Accounting Standards Codification are communicated through issuance of an Accounting Standards Update (“ASU”).  Unless otherwise discussed, we believe that the impact of recently issued guidance, whether adopted or to be adopted in the future, is not expected to be material to our consolidated financial statements upon adoption.   Offsetting Assets and Liabilities   In December 2011, the FASB issued ASU No. 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities. In January 2013, the FASB issued ASU 2013-01, Balance Sheet (Topic 210): Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities. ASU 2011-11, as clarified by ASU 2013-01, requires an entity to disclose information about offsetting and related arrangements to enable users of financial statements to understand the effect of those arrangements on its financial position, and to allow investors to better compare financial statements prepared under U.S. GAAP with financial statements prepared under International Financial Reporting Standards (IFRS). The new standards are effective for annual periods beginning January 1, 2013 and interim periods within those annual periods. Retrospective application is required.  As this accounting standard only requires enhanced disclosure, which is included in Note 4, the adoption of this standard did not impact our financial position or results of operations.   Other Comprehensive Income   In February 2013, the FASB issued ASU 2013-02, Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income.  This guidance requires disclosure of amounts reclassified out of accumulated other comprehensive income by component. In addition, an entity is required to present either on the face of the statement of operations or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income but only if the amount reclassified is required to be reclassified to net income in its entirety in the same reporting period. For amounts not reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures that provide additional detail about those amounts. This guidance is effective prospectively for annual and interim periods beginning January 1, 2013. As this accounting standard only requires enhanced disclosure, which is included in Note 12, the adoption of this standard did not impact our financial position or results of operations. </div>falsefalsefalsenonnum:textBlockItemTypenaThe entire disclosure for all significant accounting policies of the reporting entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18726-107790 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 22 -Paragraph 8 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18861-107790 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18743-107790 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18854-107790 false0Accounting Policies and Standards UpdatefalseAccounting Policies and Standards UpdateUnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.cloudpeakenergy.com/role/DisclosureAccountingPoliciesAndStandardsUpdate12