Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The significant accounting policies used in preparation of the Consolidated Financial Statements are disclosed in the Corporation’s 2021 Annual Report on Form 10-K. Those significant accounting policies are unchanged at September 30, 2022. Accounting Standards Pending Adoption ASU 2016-13: The FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, as further amended. The ASU requires credit losses on most financial assets measured at amortized cost and certain other instruments to be measured using an expected credit loss model (referred to as the current expected credit loss ("CECL") model). Under this model, entities will estimate credit losses over the entire contractual term of the instrument (considering estimated prepayments, but not expected extensions or modifications unless reasonable expectation of a troubled debt restructuring exists) from the date of initial recognition of that instrument. The ASU also replaces the current accounting model for purchased credit impaired loans and debt securities. The allowance for purchased financial assets with a more-than insignificant amount of credit deterioration since origination ("PCD assets") should be determined in a similar manner to other financial assets measured on an amortized cost basis. However, upon initial recognition, the allowance is added to the purchase price ("gross up approach") to determine the initial amortized cost basis. The subsequent accounting for PCD assets is the same expected loss model described above. Further, the ASU made certain targeted amendments to the existing impairment model for available-for-sale debt securities. For an AFS debt security for which there is neither the intent nor a more-likely-than-not requirement to sell, an entity will record credit losses as an allowance rather than a write-down of the amortized cost basis. Certain incremental disclosures are required. Subsequently, the FASB issued ASU 2018-19, ASU 2019-04, ASU 2019-05, ASU 2019-10, ASU 2019-11, and ASU 2020-02 to clarify, improve, or defer the adoption of ASU 2016-13. In October 2019, the FASB issued ASU 2019-10 which deferred the implementation date of ASU 2016-13 for smaller reporting companies (SRCs) until January 1, 2023. Mid Penn qualified as an SRC as of the most recent measurement date of September 30, 2019; therefore, Mid Penn has chosen to delay the adoption of ASU 2016-13 until January 1, 2023. Mid Penn intends to adopt this ASU effective January 1, 2023. Mid Penn expects that it is probable that total credit loss reserves will increase at the adoption date and that the magnitude of the increase will depend on the composition, characteristics and quality of its loan and lease portfolio and the allowance for debt securities, as well as economic conditions and forecasts at the time of adoption. Mid Penn is conducting parallel runs of its new processes and controls and had begun its model validation process. Mid Penn will continue to make refinements to its credit loss model in advance of the January 1, 2023 adoption date. ASU No. 2022-02: The FASB issued ASU 2022-02, Financial Instruments—Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures. This ASU eliminates the TDR recognition and measurement guidance and, instead, requires that an entity evaluate (consistent with the accounting for other loan modifications) whether a modification represents a new loan or a continuation of an existing loan. In addition, this ASU enhances existing disclosure requirements and introduces new requirements related to certain modifications of receivables made to borrowers experiencing financial difficulty. For public business entities, this ASU requires that an entity disclose current-period gross write-offs by year of origination for financing receivables and net investment in leases within the scope of Subtopic 326-20. Gross write-off information must be included in the vintage disclosures required for public business entities in accordance with paragraph 326-20-50-6, which requires that an entity disclose the amortized cost basis of financing receivables by credit quality indicator and class of financing receivable by year of origination. For entities that have adopted the amendments in update 2016-13, the amendments in this update are effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. For entities that have not yet adopted the amendments in update 2016-13, the effective dates for the amendments in this update are the same as the effective dates in Update 2016-13. The Corporation has not yet adopted this accounting standard as ASU 2016-13 has not been adopted. Management continues to evaluate the impact of its future adoption of this guidance on the Company’s financial statements.