Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2011
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements of Piedmont have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”), including the instructions to Form 10-Q and Article 10 of Regulation S-X, and do not include all of the information and footnotes required by U.S. generally accepted accounting principles (“GAAP”) for complete financial statements. In the opinion of management, the statements for the unaudited interim periods presented include all adjustments, which are of a normal and recurring nature, necessary for a fair presentation of the results for such periods. Results for these interim periods are not necessarily indicative of a full year’s results and certain prior period amounts have been reclassified to conform to the current period financial statement presentation, specifically relating to (i) the required presentation of income from discontinued operations for the 111 Sylvan Avenue Building (sold in December 2010), the Eastpointe Corporate Center (sold in July 2011), the 5000 Corporate Court Building (sold in August 2011), and the 35 W. Wacker Building (under contract as of September 30, 2011 and expected to be sold during the fourth quarter of 2011), (ii) the disclosure of Restricted cash and escrows, which was formerly a component of Prepaid expenses and other assets, and (iii) the reclassification of Class A and Class B common shares as Common Stock (see Note 12 for further detail). Piedmont’s consolidated financial statements include the accounts of Piedmont, Piedmont’s wholly-owned subsidiaries, any variable interest entity of which Piedmont or any of its wholly-owned subsidiaries is considered the primary beneficiary, or any entity in which Piedmont or any of its wholly-owned subsidiaries owns a controlling interest. For further information, refer to the financial statements and footnotes included in Piedmont’s Annual Report on Form 10-K for the year ended December 31, 2010. Further, Piedmont has formed special purpose entities to acquire and hold real estate. Each special purpose entity is a separate legal entity and consequently the assets of the special purpose entities are not available to all creditors of Piedmont. The assets owned by these special purpose entities are being reported on a consolidated basis with Piedmont’s assets for financial reporting purposes only. Income Taxes Piedmont has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), and has operated as such, beginning with its taxable year ended December 31, 1998. To qualify as a REIT, Piedmont must meet certain organizational and operational requirements, including a requirement to distribute at least 90% of its annual REIT taxable income. As a REIT, Piedmont is generally not subject to federal income taxes. Piedmont is subject to certain taxes related to the operations of properties in certain locations, as well as operations conducted by its taxable REIT subsidiary, which have been provided for in the financial statements. Interest Rate Cap Agreements Piedmont periodically enters into interest rate cap agreements to limit its exposure to changing interest rates on its variable rate debt instruments. As required by GAAP, Piedmont records all interest rate caps on the balance sheet at estimated fair value as a component of Prepaid expenses and other assets. For interest rate caps designated as cash flow hedges, Piedmont reassesses the effectiveness of its interest rate caps on a regular basis to determine if they continue to be highly effective and also to determine if the forecasted transactions remain highly probable. The changes in fair value of interest rate caps designated as cash flow hedges are recorded in other comprehensive income (“OCI”), and the option purchase premium is amortized (reclassified from OCI to interest expense) over the life of the hedging relationship as the hedged forecasted transactions affect earnings. The reclassification is based on a schedule created at the inception of the hedge, which allocates the purchase price to the future periods the hedge is expected to benefit, based on fair value as of the inception of the hedging relationship. Due to the complexities of cash flow hedge accounting, Piedmont evaluates the cost-benefit relationship between the size of the related interest rate cap agreements and the exposure to potential fluctuations in the fair value of the interest rate caps in order to determine if effective hedge accounting will be pursued. In cases where the benefit does not outweigh the costs, Piedmont elects to use mark-to-market accounting, which adjusts the interest rate cap agreements to estimated fair value through earnings on a quarterly basis. Currently, Piedmont does not use derivatives for trading or speculative purposes. Recent Accounting Pronouncements In May 2011, the Financial Accounting Standards Board ("FASB") issued an update related to Accounting Standards Codification Topic Fair Value Measurements and Disclosures (“ASC 820”) which converges GAAP and International Financial Reporting Standards ("IFRS") definition of “fair value”, the requirements for measuring amounts at fair value, and disclosures about these measurements. The update does not require additional fair value measurements and is not intended to establish valuation standards or affect valuation practices outside of financial reporting. The adoption of this update to ASC 820 is effective for Piedmont beginning with its first quarter 2012 interim financial statements and is not expected to have a material impact on Piedmont's consolidated financial statements or disclosures. In June 2011, the FASB issued a new requirement related to the presentation of Comprehensive Income ("ASC 220") intended to converge how other comprehensive income ("OCI") is presented under GAAP and IFRS. ASC 220 gives an entity the option to present OCI information in either a single continuous statement of comprehensive income or in two separate but consecutive statements, but eliminates the presentation of OCI in the statement of stockholders' equity. The adoption of ASC 220 is effective for Piedmont beginning with its first quarter 2012 interim financial statements and, as the requirement pertains to disclosure only, is not expected to have a material impact on Piedmont's consolidated financial statements. In September 2011, the FASB issued an amendment to ASC 350 regarding the testing of goodwill for impairment. Under the amended guidance, companies have the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, a company concludes that the estimated fair value is greater than the carrying amount, then performing the two-step impairment test is unnecessary. The adoption of the amendment to ASC 350 is effective for Piedmont beginning with the 2012 fiscal year, except for the specific requirement to present items that are reclassified from other comprehensive income to net income alongside their respective components of net income and other comprehensive income, which has been deferred. Early adoption of this amendment is permitted, and is not expected to have a material impact on Piedmont's consolidated financial statements or disclosures.

Summary of Significant Accounting Policies

Basis of Presentation

The consolidated financial statements of Piedmont have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”), including the instructions to Form 10-Q and Article 10 of Regulation S-X, and do not include all of the information and footnotes required by U.S. generally accepted accounting principles (“GAAP”) for complete financial statements. In the opinion of management, the statements for the unaudited interim periods presented include all adjustments, which are of a normal and recurring nature, necessary for a fair presentation of the results for such periods. Results for these interim periods are not necessarily indicative of a full year’s results and certain prior period amounts have been reclassified to conform to the current period financial statement presentation, specifically relating to (i) the required presentation of income from discontinued operations for the 111 Sylvan Avenue Building (sold in December 2010), the Eastpointe Corporate Center (sold in July 2011), the 5000 Corporate Court Building (sold in August 2011), and the 35 W. Wacker Building (under contract as of September 30, 2011 and expected to be sold during the fourth quarter of 2011), (ii) the disclosure of Restricted cash and escrows, which was formerly a component of Prepaid expenses and other assets, and (iii) the reclassification of Class A and Class B common shares as Common Stock (see Note 12 for further detail). Piedmont’s consolidated financial statements include the accounts of Piedmont, Piedmont’s wholly-owned subsidiaries, any variable interest entity of which Piedmont or any of its wholly-owned subsidiaries is considered the primary beneficiary, or any entity in which Piedmont or any of its wholly-owned subsidiaries owns a controlling interest. For further information, refer to the financial statements and footnotes included in Piedmont’s Annual Report on Form 10-K for the year ended December 31, 2010.

Further, Piedmont has formed special purpose entities to acquire and hold real estate. Each special purpose entity is a separate legal entity and consequently the assets of the special purpose entities are not available to all creditors of Piedmont. The assets owned by these special purpose entities are being reported on a consolidated basis with Piedmont’s assets for financial reporting purposes only.

Income Taxes

Piedmont has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), and has operated as such, beginning with its taxable year ended December 31, 1998. To qualify as a REIT, Piedmont must meet certain organizational and operational requirements, including a requirement to distribute at least 90% of its annual REIT taxable income. As a REIT, Piedmont is generally not subject to federal income taxes. Piedmont is subject to certain taxes related to the operations of properties in certain locations, as well as operations conducted by its taxable REIT subsidiary, which have been provided for in the financial statements.

Interest Rate Cap Agreements

Piedmont periodically enters into interest rate cap agreements to limit its exposure to changing interest rates on its variable rate debt instruments. As required by GAAP, Piedmont records all interest rate caps on the balance sheet at estimated fair value as a component of Prepaid expenses and other assets. For interest rate caps designated as cash flow hedges, Piedmont reassesses the effectiveness of its interest rate caps on a regular basis to determine if they continue to be highly effective and also to determine if the forecasted transactions remain highly probable. The changes in fair value of interest rate caps designated as cash flow hedges are recorded in other comprehensive income (“OCI”), and the option purchase premium is amortized (reclassified from OCI to interest expense) over the life of the hedging relationship as the hedged forecasted transactions affect earnings. The reclassification is based on a schedule created at the inception of the hedge, which allocates the purchase price to the future periods the hedge is expected to benefit, based on fair value as of the inception of the hedging relationship. Due to the complexities of cash flow hedge accounting, Piedmont evaluates the cost-benefit relationship between the size of the related interest rate cap agreements and the exposure to potential fluctuations in the fair value of the interest rate caps in order to determine if effective hedge accounting will be pursued. In cases where the benefit does not outweigh the costs, Piedmont elects to use mark-to-market accounting, which adjusts the interest rate cap agreements to estimated fair value through earnings on a quarterly basis. Currently, Piedmont does not use derivatives for trading or speculative purposes.

Recent Accounting Pronouncements

In May 2011, the Financial Accounting Standards Board ("FASB") issued an update related to Accounting Standards Codification Topic Fair Value Measurements and Disclosures (“ASC 820”) which converges GAAP and International Financial Reporting Standards ("IFRS") definition of “fair value”, the requirements for measuring amounts at fair value, and disclosures about these measurements. The update does not require additional fair value measurements and is not intended to establish valuation standards or affect valuation practices outside of financial reporting. The adoption of this update to ASC 820 is effective for Piedmont beginning with its first quarter 2012 interim financial statements and is not expected to have a material impact on Piedmont's consolidated financial statements or disclosures.

In June 2011, the FASB issued a new requirement related to the presentation of Comprehensive Income ("ASC 220") intended to converge how other comprehensive income ("OCI") is presented under GAAP and IFRS. ASC 220 gives an entity the option to present OCI information in either a single continuous statement of comprehensive income or in two separate but consecutive statements, but eliminates the presentation of OCI in the statement of stockholders' equity. The adoption of ASC 220 is effective for Piedmont beginning with its first quarter 2012 interim financial statements and, as the requirement pertains to disclosure only, is not expected to have a material impact on Piedmont's consolidated financial statements.

In September 2011, the FASB issued an amendment to ASC 350 regarding the testing of goodwill for impairment. Under the amended guidance, companies have the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, a company concludes that the estimated fair value is greater than the carrying amount, then performing the two-step impairment test is unnecessary. The adoption of the amendment to ASC 350 is effective for Piedmont beginning with the 2012 fiscal year, except for the specific requirement to present items that are reclassified from other comprehensive income to net income alongside their respective components of net income and other comprehensive income, which has been deferred. Early adoption of this amendment is permitted, and is not expected to have a material impact on Piedmont's consolidated financial statements or disclosures.