Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation 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 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. Piedmont’s consolidated financial statements include the accounts of Piedmont, Piedmont’s wholly-owned subsidiaries, any variable interest entity ("VIE") for which Piedmont or any of its wholly-owned subsidiaries is considered to have the power to direct the activities of the entity and the obligation to absorb losses/right to receive benefits, or any entity in which Piedmont or any of its wholly-owned subsidiaries owns a controlling interest. In determining whether Piedmont or Piedmont OP has a controlling interest, the following factors, among others, are considered: equity ownership, voting rights, protective rights of investors, and participatory rights of investors. For further information, refer to the financial statements and footnotes included in Piedmont’s Amended Annual Report on Form 10-K/A for the year ended December 31, 2016. All intercompany balances and transactions have been eliminated upon consolidation. Further, Piedmont has formed special purpose entities to acquire and hold real estate. Each special purpose entity is a separate legal entity. Consequently, the assets of these 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. Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying consolidated financial statements and notes. Actual results could differ from those estimates. Income Taxes Piedmont has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended, 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, subject to fulfilling, among other things, this distribution requirement. 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, POH, which have been provided for in the financial statements. Reclassifications Certain prior period amounts presented in Piedmont's Amended Annual Report on Form 10-K/A for the year ended December 31, 2016 have been reclassified to conform to the current period financial statement presentation. The reclassifications relate to the Two Independence Square building, located in Washington, D.C., which was first classified as held for sale as of March 31, 2017, and was sold on July 5, 2017. Applicable balances related to the same asset remain classified as held for sale as of December 31, 2016. Recent Accounting Pronouncements The Financial Accounting Standards Board (the "FASB") has issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09") and Accounting Standards Update No. 2016-08, Revenue from Contracts with Customers (Topic 606) Principal versus Agent Considerations (Reporting Revenue Gross versus Net) ("ASU 2016-08"). The amendments in ASU 2014-09, which are further clarified in ASU 2016-08, as well as Accounting Standards Update 2016-10, Accounting Standards Update 2016-12, and Accounting Standards Update 2016-20 (collectively the "Revenue Recognition Amendments"), change the criteria for the recognition of certain revenue streams to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services using a five-step determination process. Steps 1 through 5 involve (i) identifying contracts with a customer, (ii) identifying the performance obligations in the contract, (iii) determining the transaction price, (iv) allocating the transaction price to the performance obligations, and (v) recognizing revenue as an entity satisfies a performance obligation. The revenues impacted by the Revenue Recognition Amendments include a portion of Piedmont's tenant reimbursement revenues and property management fee revenues. Lease contracts and reimbursement revenues associated with property taxes and insurance are specifically excluded from the Revenue Recognition Amendments. The Revenue Recognition Amendments are effective in the first quarter of 2018 for Piedmont. Management has substantially completed its initial assessment of the impact of adoption of the Revenue Recognition Amendments. Approximately 90% of Piedmont's total revenues are derived from either long-term leases with its tenants or reimbursement of property tax and insurance expenses, which are excluded from the scope of the Revenue Recognition Amendments. In addition, based on management's assessment to date, Piedmont does not expect the timing of the recognition of reimbursement revenue and revenue from management agreements to change as a result of the new guidance, though certain classifications will change between rental revenue and tenant reimbursements. Finally, management has determined, and the FASB has confirmed, that the evaluation of non-lease components under the new Revenue Recognition Amendments will not be effective until Accounting Standards Update No. 2016-02, Leases (Topic 842), ("ASU 2016-02") becomes effective (see further discussion below), which will be first quarter of 2019 for Piedmont. Although management continues to evaluate the guidance and disclosures required by the Revenue Recognition Amendments, Piedmont does not anticipate any material impact to its consolidated financial statements as a result of adoption. The FASB has issued Accounting Standards Update No. 2017-05, Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets ("ASU 2017-05"). The provisions of ASU 2017-05 define the term "in substance nonfinancial asset" as a financial asset promised to a counterparty in a contract if substantially all of the fair value of the assets (recognized and unrecognized) is concentrated in nonfinancial assets. Further, it states that nonfinancial assets should be derecognized once the counterparty obtains control. Finally, the amendments provide clarification for partial sales of nonfinancial assets. ASU 2017-05 is effective concurrent with the Revenue Recognition Amendments (detailed above), which will be the first quarter of 2018 for Piedmont. Although management continues to evaluate the guidance and disclosures required by ASU 2017-05, Piedmont does not anticipate a material change in how it recognizes, measures, and classifies the gain or loss on the disposition of real estate in its consolidated financial statements as a result of adoption. The FASB has issued Accounting Standards Update No. 2016-01, Financial Instruments - Overall (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01"). The amendments in ASU 2016-01 require equity investments, except those accounted for under the equity method of accounting, to be measured at estimated fair value with changes in fair value recognized in net income. Additionally, ASU 2016-01 simplifies the impairment assessment of equity investments, and eliminates certain disclosure requirements. The amendments in ASU 2016-01 are effective in the first quarter of 2018, and Piedmont does not anticipate any material impact to its consolidated financial statements as a result of adoption. The FASB has issued Accounting Standards Update No. 2016-18, Statement of Cash Flows (Topic 230), Restricted Cash (a consensus of the FASB Emerging Issues Task Force) ("ASU 2016-18"). The provisions of ASU 2016-18 require entities to show changes in restricted cash and cash equivalents in addition to cash and cash equivalents in the statement of cash flows. As a result, entities will no longer present transfers between restricted and unrestricted cash in the statement of cash flows. Disclosures are required to reconcile the amount presented on the statement of cash flows to the balance sheet, as well as disclosing the nature of restriction on the restricted cash balances. ASU 2016-18 is effective for Piedmont in the first quarter of 2018, with early adoption permitted. Piedmont does not anticipate any material impact to its consolidated financial statements as a result of adoption. The FASB has issued ASU 2016-02, which fundamentally changes the definition of a lease, as well as the accounting for operating leases by requiring lessees to recognize assets and liabilities which arise from the lease, consisting of a liability to make lease payments (the lease liability) and a right-of-use asset, representing the right to use the leased asset over the term of the lease. Accounting for leases by lessors is substantially unchanged from prior practice as lessors will continue to recognize lease revenue on a straight-line basis; however, ASU 2016-02 defines certain tenant reimbursements as non-lease components which will be subject to the guidance under ASU 2014-09. The amendments in ASU 2016-02 are effective in the first quarter of 2019, and Piedmont is currently evaluating the potential impact of adoption. The FASB has issued Accounting Standards Update No. 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). The provisions of ASU 2016-13 replace the "incurred loss" approach with an "expected loss" model for impairing trade and other receivables, held-to-maturity debt securities, net investment in leases, and off-balance-sheet credit exposures, which will generally result in earlier recognition of allowances for credit losses. Additionally, the provisions change the classification of credit losses related to available-for-sale securities to an allowance, rather than a direct reduction of the amortized cost of the securities. ASU 2016-13 is effective in the first quarter of 2020, with early adoption permitted as of January 1, 2019. Piedmont is currently evaluating the potential impact of adoption. The FASB has issued Accounting Standards Update No. 2017-04, Intangibles—Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). The provisions of ASU 2017-04 simplify how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test, which is generally performed annually unless events or circumstances arise which would necessitate evaluating the carrying value for impairment in the interim. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a entity’s goodwill with the carrying amount of that goodwill by determining the fair value of its assets and liabilities (including unrecognized assets and liabilities) following the procedures that would be required in a business combination. Under the provisions of ASU 2017-04, an entity would instead recognize an impairment charge for the amount by which the carrying amount exceeds the entity’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that entity. ASU 2017-04 is effective in the first quarter of 2020, with early adoption permitted as of the first interim or annual impairment test of goodwill after January 1, 2017. Piedmont is currently evaluating the potential impact of adoption.

Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

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 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.

Piedmont’s consolidated financial statements include the accounts of Piedmont, Piedmont’s wholly-owned subsidiaries, any variable interest entity ("VIE") for which Piedmont or any of its wholly-owned subsidiaries is considered to have the power to direct the activities of the entity and the obligation to absorb losses/right to receive benefits, or any entity in which Piedmont or any of its wholly-owned subsidiaries owns a controlling interest. In determining whether Piedmont or Piedmont OP has a controlling interest, the following factors, among others, are considered: equity ownership, voting rights, protective rights of investors, and participatory rights of investors. For further information, refer to the financial statements and footnotes included in Piedmont’s Amended Annual Report on Form 10-K/A for the year ended December 31, 2016.

All intercompany balances and transactions have been eliminated upon consolidation.

Further, Piedmont has formed special purpose entities to acquire and hold real estate. Each special purpose entity is a separate legal entity. Consequently, the assets of these 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.

Use of Estimates

The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying consolidated financial statements and notes. Actual results could differ from those estimates.

Income Taxes

Piedmont has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended, 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, subject to fulfilling, among other things, this distribution requirement. 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, POH, which have been provided for in the financial statements.

Reclassifications

Certain prior period amounts presented in Piedmont's Amended Annual Report on Form 10-K/A for the year ended December 31, 2016 have been reclassified to conform to the current period financial statement presentation. The reclassifications relate to the Two Independence Square building, located in Washington, D.C., which was first classified as held for sale as of March 31, 2017, and was sold on July 5, 2017. Applicable balances related to the same asset remain classified as held for sale as of December 31, 2016.

Recent Accounting Pronouncements

The Financial Accounting Standards Board (the "FASB") has issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09") and Accounting Standards Update No. 2016-08, Revenue from Contracts with Customers (Topic 606) Principal versus Agent Considerations (Reporting Revenue Gross versus Net) ("ASU 2016-08"). The amendments in ASU 2014-09, which are further clarified in ASU 2016-08, as well as Accounting Standards Update 2016-10, Accounting Standards Update 2016-12, and Accounting Standards Update 2016-20 (collectively the "Revenue Recognition Amendments"), change the criteria for the recognition of certain revenue streams to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services using a five-step determination process. Steps 1 through 5 involve (i) identifying contracts with a customer, (ii) identifying the performance obligations in the contract, (iii) determining the transaction price, (iv) allocating the transaction price to the performance obligations, and (v) recognizing revenue as an entity satisfies a performance obligation. The revenues impacted by the Revenue Recognition Amendments include a portion of Piedmont's tenant reimbursement revenues and property management fee revenues. Lease contracts and reimbursement revenues associated with property taxes and insurance are specifically excluded from the Revenue Recognition Amendments. The Revenue Recognition Amendments are effective in the first quarter of 2018 for Piedmont. Management has substantially completed its initial assessment of the impact of adoption of the Revenue Recognition Amendments. Approximately 90% of Piedmont's total revenues are derived from either long-term leases with its tenants or reimbursement of property tax and insurance expenses, which are excluded from the scope of the Revenue Recognition Amendments. In addition, based on management's assessment to date, Piedmont does not expect the timing of the recognition of reimbursement revenue and revenue from management agreements to change as a result of the new guidance, though certain classifications will change between rental revenue and tenant reimbursements. Finally, management has determined, and the FASB has confirmed, that the evaluation of non-lease components under the new Revenue Recognition Amendments will not be effective until Accounting Standards Update No. 2016-02, Leases (Topic 842), ("ASU 2016-02") becomes effective (see further discussion below), which will be first quarter of 2019 for Piedmont. Although management continues to evaluate the guidance and disclosures required by the Revenue Recognition Amendments, Piedmont does not anticipate any material impact to its consolidated financial statements as a result of adoption.

The FASB has issued Accounting Standards Update No. 2017-05, Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets ("ASU 2017-05"). The provisions of ASU 2017-05 define the term "in substance nonfinancial asset" as a financial asset promised to a counterparty in a contract if substantially all of the fair value of the assets (recognized and unrecognized) is concentrated in nonfinancial assets. Further, it states that nonfinancial assets should be derecognized once the counterparty obtains control. Finally, the amendments provide clarification for partial sales of nonfinancial assets. ASU 2017-05 is effective concurrent with the Revenue Recognition Amendments (detailed above), which will be the first quarter of 2018 for Piedmont. Although management continues to evaluate the guidance and disclosures required by ASU 2017-05, Piedmont does not anticipate a material change in how it recognizes, measures, and classifies the gain or loss on the disposition of real estate in its consolidated financial statements as a result of adoption.

The FASB has issued Accounting Standards Update No. 2016-01, Financial Instruments - Overall (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01"). The amendments in ASU 2016-01 require equity investments, except those accounted for under the equity method of accounting, to be measured at estimated fair value with changes in fair value recognized in net income. Additionally, ASU 2016-01 simplifies the impairment assessment of equity investments, and eliminates certain disclosure requirements. The amendments in ASU 2016-01 are effective in the first quarter of 2018, and Piedmont does not anticipate any material impact to its consolidated financial statements as a result of adoption.

The FASB has issued Accounting Standards Update No. 2016-18, Statement of Cash Flows (Topic 230), Restricted Cash (a consensus of the FASB Emerging Issues Task Force) ("ASU 2016-18"). The provisions of ASU 2016-18 require entities to show changes in restricted cash and cash equivalents in addition to cash and cash equivalents in the statement of cash flows. As a result, entities will no longer present transfers between restricted and unrestricted cash in the statement of cash flows. Disclosures are required to reconcile the amount presented on the statement of cash flows to the balance sheet, as well as disclosing the nature of restriction on the restricted cash balances. ASU 2016-18 is effective for Piedmont in the first quarter of 2018, with early adoption permitted. Piedmont does not anticipate any material impact to its consolidated financial statements as a result of adoption.

The FASB has issued ASU 2016-02, which fundamentally changes the definition of a lease, as well as the accounting for operating leases by requiring lessees to recognize assets and liabilities which arise from the lease, consisting of a liability to make lease payments (the lease liability) and a right-of-use asset, representing the right to use the leased asset over the term of the lease. Accounting for leases by lessors is substantially unchanged from prior practice as lessors will continue to recognize lease revenue on a straight-line basis; however, ASU 2016-02 defines certain tenant reimbursements as non-lease components which will be subject to the guidance under ASU 2014-09. The amendments in ASU 2016-02 are effective in the first quarter of 2019, and Piedmont is currently evaluating the potential impact of adoption.

The FASB has issued Accounting Standards Update No. 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). The provisions of ASU 2016-13 replace the "incurred loss" approach with an "expected loss" model for impairing trade and other receivables, held-to-maturity debt securities, net investment in leases, and off-balance-sheet credit exposures, which will generally result in earlier recognition of allowances for credit losses. Additionally, the provisions change the classification of credit losses related to available-for-sale securities to an allowance, rather than a direct reduction of the amortized cost of the securities. ASU 2016-13 is effective in the first quarter of 2020, with early adoption permitted as of January 1, 2019. Piedmont is currently evaluating the potential impact of adoption.

The FASB has issued Accounting Standards Update No. 2017-04, Intangibles—Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). The provisions of ASU 2017-04 simplify how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test, which is generally performed annually unless events or circumstances arise which would necessitate evaluating the carrying value for impairment in the interim. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a entity’s goodwill with the carrying amount of that goodwill by determining the fair value of its assets and liabilities (including unrecognized assets and liabilities) following the procedures that would be required in a business combination. Under the provisions of ASU 2017-04, an entity would instead recognize an impairment charge for the amount by which the carrying amount exceeds the entity’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that entity. ASU 2017-04 is effective in the first quarter of 2020, with early adoption permitted as of the first interim or annual impairment test of goodwill after January 1, 2017. Piedmont is currently evaluating the potential impact of adoption.