Accounting Standards Updates	9 Months Ended
Sep. 30, 2018
Accounting Policies [Abstract]
Accounting Standards Updates	Accounting Standards Updates Newly Adopted Accounting Standards In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers” ("ASC 606"). The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies generally will be required to use more judgment and make more estimates than under current guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. For financial reporting purposes, the standard allows for either full retrospective adoption, meaning the standard is applied to all of the periods presented, or modified retrospective adoption, meaning the standard is applied only to the most current period presented in the financial statements with the cumulative effect of initially applying the standard recognized at the date of initial application. Since the guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other GAAP, the new guidance did not have a material impact on revenue most closely associated with financial instruments, including interest income and expense. The Company completed its overall assessment of revenue streams and review of related contracts potentially affected by the ASU, including trust and asset management fees, deposit related fees, interchange fees, merchant income, and annuity and insurance commissions. On January 1, 2018, the Company adopted ASC 606 using the modified retrospective method for all contracts. Results for reporting periods beginning January 1, 2018 are presented under ASC 606, while prior period amounts were not adjusted and continue to be reported in accordance with the Company’s historic accounting under Topic 605, Revenue Recognition. The Company recorded a net increase to beginning retained earnings of $1.8 million as of January 1, 2018 due to the cumulative impact of adopting ASC 606. The impact to beginning retained earnings was primarily driven by the recognition of $1.8 million of contingency income related to our insurance business segment. The adoption of ASC 606 did not have a significant impact on the Company’s consolidated financial statements as of and for the three and nine months ended September 30, 2018 and, as a result, comparisons of revenues and operating profit performance between periods are not significantly affected by the adoption of this ASU. Refer to Note 11 "Revenue Recognition" for additional disclosures required by ASC 606. In January 2016, the FASB issued ASU No. 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities.” This ASU addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments by making targeted improvements to GAAP as follows: (1) require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer; (2) simplify the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment. When a qualitative assessment indicates that impairment exists, an entity is required to measure the investment at fair value; (3) eliminate the requirement to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities; (4) eliminate the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; (5) require public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; (6) require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; (7) require separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (that is, securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; and (8) clarify that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. The Company adopted ASU No. 2016-01 effective January 1, 2018, and recognized a cumulative-effect adjustment of $65,000 for the after-tax impact of the unrealized loss on equity securities. In addition, the Company measured the fair value of its loan portfolio as of September 30, 2018 using an exit price notion. Refer to Note 14 "Fair Value". In August 2016, the FASB issued ASU No. 2016-15, “Classification of Certain Cash Receipts and Cash Payments.” ASU 2016-15 provides guidance related to certain cash flow issues in order to reduce the current and potential future diversity in practice. The Company adopted ASU No. 2016-15 on January 1, 2018. ASU No. 2016-15 did not have a material impact on the Company’s consolidated financial statements. In March 2017, the FASB issued ASU No. 2017-07, “Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” Under the new guidance, employers are required to present the service cost component of the net periodic benefit cost in the same income statement line item (e.g., Salaries and Benefits) as other employee compensation costs arising from services rendered during the period. In addition, only the service cost component will be eligible for capitalization in assets. Employers will present the other components of net periodic benefit cost separately (e.g., Other Noninterest Expense) from the line item that includes the service cost. ASU No. 2017-07 is effective for interim and annual reporting periods beginning after December 15, 2017. Employers will apply the guidance on the presentation of the components of net periodic benefit cost in the income statement retrospectively. The guidance limiting the capitalization of net periodic benefit cost in assets to the service cost component will be applied prospectively. The Company adopted ASU No. 2017-07 on January 1, 2018 and utilized the ASU’s practical expedient allowing entities to estimate amounts for comparative periods using the information previously disclosed in their pension and other postretirement benefit plan footnote. ASU No. 2017-07 did not have a material impact on the Company’s consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, “Compensation-Stock Compensation (Topic 718)- Scope of Modification Accounting.” ASU 2017-09 clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. Under ASU 2017-09, an entity will not apply modification accounting to a share-based payment award if all of the following are the same immediately before and after the change: (i) the award's fair value, (ii) the award's vesting conditions and (iii) the award's classification as an equity or liability instrument. ASU 2017-09 became effective for us on January 1, 2018 and did not have a significant impact on our consolidated financial statements. ASU 2018-02, "Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" was issued to address a narrow-scope financial reporting issue that arose as a consequence of the change in the tax law. On December 22, 2017, the U.S. federal government enacted a tax bill, H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018 (Tax Cuts and Jobs Act of 2017). ASU 2018-02 allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the newly enacted federal corporate income tax rate. The amount of the reclassification would be the difference between the historical corporate income tax rate of 35 percent and the newly enacted 21 percent corporate income tax rate. ASU 2018-02 is effective for all entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted, including adoption in any interim period, for (i) public business entities for reporting periods for which financial statements have not yet been issued and (ii) all other entities for reporting periods for which financial statements have not yet been made available for issuance. The changes are applied retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act of 2017 is recognized. The Company early adopted ASU 2018-02 in 2017, which resulted in the reclassification from accumulated other comprehensive income (loss) to retained earnings totaling $10.0 million, reflected in the consolidated statements of changes in shareholders' equity. ASU 2018-05, "Income Taxes (Topic 740) - Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118." ASU 2018-05 amends the Accounting Standards Codification to incorporate various SEC paragraphs pursuant to the issuance of SAB 118. SAB 118 addresses the application of generally accepted accounting principles in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act of 2017. Accounting Standards Pending Adoption Information about certain recently issued accounting standards updates is presented below. Also refer to Note 1 - "Summary of Significant Accounting Policies" in our 2017 Form 10-K for additional information related to previously issued accounting standards updates. ASU 2016-02,“Leases (Topic 842).” ASU 2016-02 will, among other things, require lessees to recognize a lease liability, which is a lessee‘s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model and ASC Topic 606, “Revenue from Contracts with Customers.” ASU 2016-2 will be effective for Tompkins on January 1, 2019 and will require transition using a modified retrospective approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company occupies certain banking offices and uses certain equipment under noncancelable operating lease agreements, which currently are not reflected in its consolidated statements of condition. Tompkins is preparing an inventory of its leases and evaluating the impact of this ASU on these leases. Upon adoption of the guidance, the Company expects to report increased assets and increased liabilities as a result of recognizing right-of-use assets and lease liabilities on its consolidated statements of condition. Tompkins is currently evaluating the extent of the impact that the adoption of this ASU will have on our consolidated financial statements. ASU No. 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective on January 1, 2020. Tompkins is currently evaluating the requirements of the new guidance to determine what modifications to our existing allowance methodology may be required. The Company expects that the new guidance will likely result in an increase in the allowance; however, Tompkins is unable to quantify the impact at this time since we are still reviewing the guidance. The extent of any impact to our allowance will depend, in part, upon the composition of our loan portfolio at the adoption date as well as economic conditions and loss forecasts at that date. ASU 2017-08 “Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20) - Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium to require such premiums to be amortized to the earliest call date unless applicable guidance related to certain pools of securities is applied to consider estimated prepayments. Under prior guidance, entities were generally required to amortize premiums on individual, non-pooled callable debt securities as a yield adjustment over the contractual life of the security. ASU 2017-08 does not change the accounting for callable debt securities held at a discount. ASU 2017-08 will be effective for us on January 1, 2019, with early adoption permitted. Tompkins is currently evaluating the potential impact of ASU 2017-08 on our consolidated financial statements.

Accounting Standards Updates

Newly Adopted Accounting Standards

In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers” ("ASC 606"). The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies generally will be required to use more judgment and make more estimates than under current guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. For financial reporting purposes, the standard allows for either full retrospective adoption, meaning the standard is applied to all of the periods presented, or modified retrospective adoption, meaning the standard is applied only to the most current period presented in the financial statements with the cumulative effect of initially applying the standard recognized at the date of initial application. Since the guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other GAAP, the new guidance did not have a material impact on revenue most closely associated with financial instruments, including interest income and expense. The Company completed its overall assessment of revenue streams and review of related contracts potentially affected by the ASU, including trust and asset management fees, deposit related fees, interchange fees, merchant income, and annuity and insurance commissions.

On January 1, 2018, the Company adopted ASC 606 using the modified retrospective method for all contracts. Results for reporting periods beginning January 1, 2018 are presented under ASC 606, while prior period amounts were not adjusted and continue to be reported in accordance with the Company’s historic accounting under Topic 605, Revenue Recognition.

The Company recorded a net increase to beginning retained earnings of $1.8 million as of January 1, 2018 due to the cumulative impact of adopting ASC 606. The impact to beginning retained earnings was primarily driven by the recognition of $1.8 million of contingency income related to our insurance business segment. The adoption of ASC 606 did not have a significant impact on the Company’s consolidated financial statements as of and for the three and nine months ended September 30, 2018 and, as a result, comparisons of revenues and operating profit performance between periods are not significantly affected by the adoption of this ASU. Refer to Note 11 "Revenue Recognition" for additional disclosures required by ASC 606.

In January 2016, the FASB issued ASU No. 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities.” This ASU addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments by making targeted improvements to GAAP as follows: (1) require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer; (2) simplify the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment. When a qualitative assessment indicates that impairment exists, an entity is required to measure the investment at fair value; (3) eliminate the requirement to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities; (4) eliminate the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; (5) require public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; (6) require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; (7) require separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (that is, securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; and (8) clarify that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. The Company adopted ASU No. 2016-01 effective January 1, 2018, and recognized a cumulative-effect adjustment of $65,000 for the after-tax impact of the unrealized loss on equity securities. In addition, the Company measured the fair value of its loan portfolio as of September 30, 2018 using an exit price notion. Refer to Note 14 "Fair Value".

In August 2016, the FASB issued ASU No. 2016-15, “Classification of Certain Cash Receipts and Cash Payments.” ASU 2016-15 provides guidance related to certain cash flow issues in order to reduce the current and potential future diversity in practice. The Company adopted ASU No. 2016-15 on January 1, 2018. ASU No. 2016-15 did not have a material impact on the Company’s consolidated financial statements.

In March 2017, the FASB issued ASU No. 2017-07, “Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” Under the new guidance, employers are required to present the service cost component of the net periodic benefit cost in the same income statement line item (e.g., Salaries and Benefits) as other employee compensation costs arising from services rendered during the period. In addition, only the service cost component will be eligible for capitalization in assets. Employers will present the other components of net periodic benefit cost separately (e.g., Other Noninterest Expense) from the line item that includes the service cost. ASU No. 2017-07 is effective for interim and annual reporting periods beginning after December 15, 2017. Employers will apply the guidance on the presentation of the components of net periodic benefit cost in the income statement retrospectively. The guidance limiting the capitalization of net periodic benefit cost in assets to the service cost component will be applied prospectively. The Company adopted ASU No. 2017-07 on January 1, 2018 and utilized the ASU’s practical expedient allowing entities to estimate amounts for comparative periods using the information previously disclosed in their pension and other postretirement benefit plan footnote. ASU No. 2017-07 did not have a material impact on the Company’s consolidated financial statements.

In May 2017, the FASB issued ASU 2017-09, “Compensation-Stock Compensation (Topic 718)- Scope of Modification Accounting.” ASU 2017-09 clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. Under ASU 2017-09, an entity will not apply modification accounting to a share-based payment award if all of the following are the same immediately before and after the change: (i) the award's fair value, (ii) the award's vesting conditions and (iii) the award's classification as an equity or liability instrument. ASU 2017-09 became effective for us on January 1, 2018 and did not have a significant impact on our consolidated financial statements.

ASU 2018-02, "Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" was issued to address a narrow-scope financial reporting issue that arose as a consequence of the change in the tax law. On December 22, 2017, the U.S. federal government enacted a tax bill, H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018 (Tax Cuts and Jobs Act of 2017). ASU 2018-02 allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the newly enacted federal corporate income tax rate. The amount of the reclassification would be the difference between the historical corporate income tax rate of 35 percent and the newly enacted 21 percent corporate income tax rate. ASU 2018-02 is effective for all entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted, including adoption in any interim period, for (i) public business entities for reporting periods for which financial statements have not yet been issued and (ii) all other entities for reporting periods for which financial statements have not yet been made available for issuance. The changes are applied retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act of 2017 is recognized. The Company early adopted ASU 2018-02 in 2017, which resulted in the reclassification from accumulated other comprehensive income (loss) to retained earnings totaling $10.0 million, reflected in the consolidated statements of changes in shareholders' equity.

ASU 2018-05, "Income Taxes (Topic 740) - Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118." ASU 2018-05 amends the Accounting Standards Codification to incorporate various SEC paragraphs pursuant to the issuance of SAB 118. SAB 118 addresses the application of generally accepted accounting principles in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act of 2017.

Accounting Standards Pending Adoption

Information about certain recently issued accounting standards updates is presented below. Also refer to Note 1 - "Summary of Significant Accounting Policies" in our 2017 Form 10-K for additional information related to previously issued accounting standards updates.

ASU 2016-02,“Leases (Topic 842).” ASU 2016-02 will, among other things, require lessees to recognize a lease liability, which is a lessee‘s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model and ASC Topic 606, “Revenue from Contracts with Customers.” ASU 2016-2 will be effective for Tompkins on January 1, 2019 and will require transition using a modified retrospective approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company occupies certain banking offices and uses certain equipment under noncancelable operating lease agreements, which currently are not reflected in its consolidated statements of condition. Tompkins is preparing an inventory of its leases and evaluating the impact of this ASU on these leases. Upon adoption of the guidance, the Company expects to report increased assets and increased liabilities as a result of recognizing right-of-use assets and lease liabilities on its consolidated statements of condition. Tompkins is currently evaluating the extent of the impact that the adoption of this ASU will have on our consolidated financial statements.

ASU No. 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective on January 1, 2020. Tompkins is currently evaluating the requirements of the new guidance to determine what modifications to our existing allowance methodology may be required. The Company expects that the new guidance will likely result in an increase in the allowance; however, Tompkins is unable to quantify the impact at this time since we are still reviewing the guidance. The extent of any impact to our allowance will depend, in part, upon the composition of our loan portfolio at the adoption date as well as economic conditions and loss forecasts at that date.

ASU 2017-08 “Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20) - Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium to require such premiums to be amortized to the earliest call date unless applicable guidance related to certain pools of securities is applied to consider estimated prepayments. Under prior guidance, entities were generally required to amortize premiums on individual, non-pooled callable debt securities as a yield adjustment over the contractual life of the security. ASU 2017-08 does not change the accounting for callable debt securities held at a discount. ASU 2017-08 will be effective for us on January 1, 2019, with early adoption permitted. Tompkins is currently evaluating the potential impact of ASU 2017-08 on our consolidated financial statements.