Basis of Presentation	9 Months Ended
Sep. 30, 2011
Basis of Presentation [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	BASIS OF PRESENTATION Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America and with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim financial reporting, and include all adjustments which are, in the opinion of management, necessary for a fair presentation. The financial statements require the use of management estimates and include the accounts of the Company, its controlled subsidiaries and other entities consolidated as required by accounting principles generally accepted in the United States of America (“GAAP”). References to the “Company,” “its” and “itself,” refer to Duff & Phelps Corporation and its subsidiaries, unless the context requires otherwise. The balance sheet at December 31, 2010 was derived from audited financial statements, but does not include all disclosures required by GAAP. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In management's opinion, all adjustments necessary for a fair presentation are reflected in the interim periods presented. All significant intercompany accounts and transactions have been eliminated in consolidation. Recent Accounting Pronouncements Effective January 1, 2011, the Company adopted the Financial Accounting Standards Board's (“FASB”) Accounting Standards Update (“ASU”) No. 2009-13, Revenue Recognition (Topic 605): Multiple-Deliverable Revenue Arrangements. ASU 2009-13 supersedes certain guidance in FASB ASC 605-25, Revenue Recognition-Multiple-Element Arrangements and requires an entity to allocate arrangement consideration at the inception of an arrangement to all of its deliverables based on their relative selling prices (the relative-selling-price method). ASU 2009-13 eliminates the use of the residual method of allocation in which the undelivered element is measured at its estimated selling price and the delivered element is measured as the residual of the arrangement consideration, and requires the relative-selling-price method in all circumstances in which an entity recognizes revenue for an arrangement with multiple deliverable subject to ASU 2009-13. The adoption of ASU 2009-13 did not have a material effect on the Company's consolidated financial statements. In May 2011, the FASB issued Accounting Standards Update ("ASU") No. 2011-04, Fair Value Measurement (Topic 820): Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs. This update is the result of the work by the FASB and the International Accounting Standards Board ("IASB") to develop common requirements for measuring fair value and for disclosing information about fair value measurements in accordance with GAAP and International Financial Reporting Standards ("IFRSs"). The amendments in this update explain how to measure fair value. They do not require additional fair value measurements and are not intended to establish valuation standards or affect valuation practices outside of financial reporting. The amendments in this update become effective during interim and annual periods beginning after December 15, 2011. The Company does not anticipate that the adoption of ASU 2011-04 will have a material effect on its consolidated financial statements. In June 2011, the FASB issued ASU 2011-05, Comprehensive Income (Topic 220): Presentation of Comprehensive Income. This update revises the manner in which entities present comprehensive income in their financial statements. The guidance removes the presentation options in ASC 220 and requires entities to report components of comprehensive income in either (1) a continuous statement of comprehensive income or (2) two separate but consecutive statements. Under the two-statement approach, the first statement would include components of net income, which is consistent with the income statement format used today, and the second statement would include components of other comprehensive income ("OCI"). The ASU does not change the items that must be reported in OCI. The FASB's issuance of ASU 2011-05 represents another step toward its goal of convergence with IFRSs. The amendments in this update should be applied retrospectively and are effective for fiscal years and interim periods within those years beginning after December 15, 2011. The Company does not anticipate that the adoption of ASU 2011-05 will have a material effect on its consolidated financial statements. In September 2011, the FASB issued ASU 2011-08, Intangibles-Goodwill and Other (Topic 350): Testing Goodwill for Impairment. The update permits an entity to first assess qualitative factors to determine whether it is necessary to perform the two-step goodwill impairment test. If an entity determines based on qualitative factors that it is not more likely than not that a reporting unit's fair value is less than its carrying amount, then the two step impairment test will be unnecessary. The amendment will be effective for interim and annual goodwill impairment tests performed for fiscal years beginning after December 15, 2011. The Company does not anticipate that the adoption of ASU 2011-08 will have a material effect on its consolidated financial statements. Critical Accounting Policies There have been no significant changes in new accounting pronouncements or in our critical accounting policies and estimates from those that were disclosed in our Annual Report on Form 10-K for the year ended December 31, 2010. The Company believes that the disclosures herein are adequate so that the information presented is not misleading; however, it is suggested that these financial statements be read in conjunction with the financial statements and the notes thereto in our Annual Report on Form 10-K for the year ended December 31, 2010. The financial data for the interim periods may not necessarily be indicative of results to be expected for the year.

BASIS OF PRESENTATION

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America and with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim financial reporting, and include all adjustments which are, in the opinion of management, necessary for a fair presentation. The financial statements require the use of management estimates and include the accounts of the Company, its controlled subsidiaries and other entities consolidated as required by accounting principles generally accepted in the United States of America (“GAAP”). References to the “Company,” “its” and “itself,” refer to Duff & Phelps Corporation and its subsidiaries, unless the context requires otherwise.

The balance sheet at December 31, 2010 was derived from audited financial statements, but does not include all disclosures required by GAAP. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In management's opinion, all adjustments necessary for a fair presentation are reflected in the interim periods presented. All significant intercompany accounts and transactions have been eliminated in consolidation.

Recent Accounting Pronouncements

Effective January 1, 2011, the Company adopted the Financial Accounting Standards Board's (“FASB”) Accounting Standards Update (“ASU”) No. 2009-13, Revenue Recognition (Topic 605): Multiple-Deliverable Revenue Arrangements. ASU 2009-13 supersedes certain guidance in FASB ASC 605-25, Revenue Recognition-Multiple-Element Arrangements and requires an entity to allocate arrangement consideration at the inception of an arrangement to all of its deliverables based on their relative selling prices (the relative-selling-price method). ASU 2009-13 eliminates the use of the residual method of allocation in which the undelivered element is measured at its estimated selling price and the delivered element is measured as the residual of the arrangement consideration, and requires the relative-selling-price method in all circumstances in which an entity recognizes revenue for an arrangement with multiple deliverable subject to ASU 2009-13. The adoption of ASU 2009-13 did not have a material effect on the Company's consolidated financial statements.

In May 2011, the FASB issued Accounting Standards Update ("ASU") No. 2011-04, Fair Value Measurement (Topic 820): Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs. This update is the result of the work by the FASB and the International Accounting Standards Board ("IASB") to develop common requirements for measuring fair value and for disclosing information about fair value measurements in accordance with GAAP and International Financial Reporting Standards ("IFRSs"). The amendments in this update explain how to measure fair value. They do not require additional fair value measurements and are not intended to establish valuation standards or affect valuation practices outside of financial reporting. The amendments in this update become effective during interim and annual periods beginning after December 15, 2011. The Company does not anticipate that the adoption of ASU 2011-04 will have a material effect on its consolidated financial statements.

In June 2011, the FASB issued ASU 2011-05, Comprehensive Income (Topic 220): Presentation of Comprehensive Income. This update revises the manner in which entities present comprehensive income in their financial statements. The guidance removes the presentation options in ASC 220 and requires entities to report components of comprehensive income in either (1) a continuous statement of comprehensive income or (2) two separate but consecutive statements. Under the two-statement approach, the first statement would include components of net income, which is consistent with the income statement format used today, and the second statement would include components of other comprehensive income ("OCI"). The ASU does not change the items that must be reported in OCI. The FASB's issuance of ASU 2011-05 represents another step toward its goal of convergence with IFRSs. The amendments in this update should be applied retrospectively and are effective for fiscal years and interim periods within those years beginning after December 15, 2011. The Company does not anticipate that the adoption of ASU 2011-05 will have a material effect on its consolidated financial statements.

In September 2011, the FASB issued ASU 2011-08, Intangibles-Goodwill and Other (Topic 350): Testing Goodwill for Impairment. The update permits an entity to first assess qualitative factors to determine whether it is necessary to perform the two-step goodwill impairment test. If an entity determines based on qualitative factors that it is not more likely than not that a reporting unit's fair value is less than its carrying amount, then the two step impairment test will be unnecessary. The amendment will be effective for interim and annual goodwill impairment tests performed for fiscal years beginning after December 15, 2011. The Company does not anticipate that the adoption of ASU 2011-08 will have a material effect on its consolidated financial statements.

Critical Accounting Policies

There have been no significant changes in new accounting pronouncements or in our critical accounting policies and estimates from those that were disclosed in our Annual Report on Form 10-K for the year ended December 31, 2010. The Company believes that the disclosures herein are adequate so that the information presented is not misleading; however, it is suggested that these financial statements be read in conjunction with the financial statements and the notes thereto in our Annual Report on Form 10-K for the year ended December 31, 2010. The financial data for the interim periods may not necessarily be indicative of results to be expected for the year.