Accounting Standards Updates (Policies)	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
New Adopted Accounting Standards and Accounting Standards Pending Adoption	Newly Adopted Accounting Standards In February 2016, the FASB issued ASU No. 2016-02, “Leases.” Under the new guidance, lessees are required to recognize the following for all leases: 1) a lease liability, which is the present value of a lessee’s obligation to make lease payments, and 2) 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. Lessor accounting under the new guidance remains largely unchanged as it is substantially equivalent to existing guidance for sales-type leases, direct financing leases, and operating leases. Leveraged leases have been eliminated, although lessors can continue to account for existing leveraged leases using the current accounting guidance. Other limited changes were made to align lessor accounting with the lessee accounting model and the new revenue recognition standard. All entities will classify leases to determine how to recognize lease-related revenue and expense. Quantitative and qualitative disclosures are required by lessees and lessors to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The intention is to require enough information to supplement the amounts recorded in the financial statements so that users can understand more about the nature of an entity’s leasing activities. ASU No. 2016-02 is effective for interim and annual reporting periods beginning after December 15, 2018. All entities are required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. As the Company elected the transition option provided in ASU No. 2018-11 (see below), the modified retrospective approach was applied on January 1, 2019 (as opposed to January 1, 2017). The Company also elected certain relief options offered in ASU 2016-02 including the package of practical expedients, however the Company has chosen to continue to separate lease and non-lease components instead of accounting for them as a single lease component. The Company did not elect the hindsight practical expedient, which allows entities to use hindsight when determining lease term and impairment of right-of-use assets. The Company has several lease agreements, such as leases for branch locations, which are considered operating leases, and therefore, were not previously recognized on the Company’s consolidated statements of condition. The new guidance requires these lease agreements to be recognized on the consolidated statements of condition as a right-of-use asset and a corresponding lease liability. The new guidance did not have a material impact on the consolidated statements of income or the consolidated statements of cash flows. See Note 15 - "Leases" for more information. In July 2018, the FASB issued ASU No. 2018-11, “Leases - Targeted Improvements” to provide entities with relief from the costs of implementing certain aspects of the new leasing standard, ASU No. 2016-02. Specifically, under the amendments in ASU 2018-11: (1) entities may elect not to recast the comparative periods presented when transitioning to the new leasing standard, and (2) lessors may elect not to separate lease and non-lease components when certain conditions are met. The amendments have the same effective date as ASU 2016-02 (January 1, 2019 for the Company). The Company adopted ASU 2018-11 on its required effective date of January 1, 2019 and elected both transition options mentioned above. ASU 2018-11 did not have a material impact on the Company’s Consolidated Financial Statements. In December 2018, the FASB issued ASU No. 2018-20, “Narrow-Scope Improvements for Lessors.” This ASU (1) allows lessors to make an accounting policy election of presenting sales taxes and other similar taxes collected from lessees on a net basis, (2) requires a lessor to exclude lessor costs paid directly by a lessee to third parties on the lessor’s behalf and include lessor costs that are paid by the lessor and reimbursed by the lessee in the measurement of variable lease revenue and the associated expense, and (3) clarifies that when lessors allocate variable payments to lease and non-lease components they are required to follow the recognition guidance in the new leases standard for the lease component and other applicable guidance, such as the new revenue standard, for the non-lease component. The Company adopted ASU 2018-20 on its required effective date of January 1, 2019 and its adoption did not have a material impact on the Company’s Consolidated Financial Statements. In March 2019, the FASB issued ASU No. 2019-01, “Leases: Codification Improvements.” This ASU (1) states that for lessors that are not manufacturers or dealers, the fair value of the underlying asset is its cost, less any volume or trade discounts, as long as there is not a significant amount of time between acquisition of the asset and lease commencement; (2) clarifies that lessors in the scope of ASC 942 (such as the Company) must classify principal payments received from sales-type and direct financing leases in investing activities in the statement of cash flows; and (3) clarifies the transition guidance related to certain interim disclosures provided in the year of adoption. To coincide with the adoption of ASU No. 2016-02, the Company elected to early adopt ASU 2019-01 on January 1, 2019. The adoption of this ASU did not have a material impact on the Company’s Consolidated Financial Statements. 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 became effective for us on January 1, 2019 and did not have a significant impact on the Company's Consolidated Financial Statements. 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 2018 Form 10-K for additional information related to previously issued accounting standards updates. 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. 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.

Newly Adopted Accounting Standards

In February 2016, the FASB issued ASU No. 2016-02, “Leases.” Under the new guidance, lessees are required to recognize the following for all leases: 1) a lease liability, which is the present value of a lessee’s obligation to make lease payments, and 2) 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. Lessor accounting under the new guidance remains largely unchanged as it is substantially equivalent to existing guidance for sales-type leases, direct financing leases, and operating leases. Leveraged leases have been eliminated, although lessors can continue to account for existing leveraged leases using the current accounting guidance. Other limited changes were made to align lessor accounting with the lessee accounting model and the new revenue recognition standard. All entities will classify leases to determine how to recognize lease-related revenue and expense. Quantitative and qualitative disclosures are required by lessees and lessors to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The intention is to require enough information to supplement the amounts recorded in the financial statements so that users can understand more about the nature of an entity’s leasing activities. ASU No. 2016-02 is effective for interim and annual reporting periods beginning after December 15, 2018. All entities are required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. As the Company elected the transition option provided in ASU No. 2018-11 (see below), the modified retrospective approach was applied on January 1, 2019 (as opposed to January 1, 2017). The Company also elected certain relief options offered in ASU 2016-02 including the package of practical expedients, however the Company has chosen to continue to separate lease and non-lease components instead of accounting for them as a single lease component. The Company did not elect the hindsight practical expedient, which allows entities to use hindsight when determining lease term and impairment of right-of-use assets. The Company has several lease agreements, such as leases for branch locations, which are considered operating leases, and therefore, were not previously recognized on the Company’s consolidated statements of condition. The new guidance requires these lease agreements to be recognized on the consolidated statements of condition as a right-of-use asset and a corresponding lease liability. The new guidance did not have a material impact on the consolidated statements of income or the consolidated statements of cash flows. See Note 15 - "Leases" for more information.

In July 2018, the FASB issued ASU No. 2018-11, “Leases - Targeted Improvements” to provide entities with relief from the costs of implementing certain aspects of the new leasing standard, ASU No. 2016-02. Specifically, under the amendments in ASU 2018-11: (1) entities may elect not to recast the comparative periods presented when transitioning to the new leasing standard, and (2) lessors may elect not to separate lease and non-lease components when certain conditions are met. The amendments have the same effective date as ASU 2016-02 (January 1, 2019 for the Company). The Company adopted ASU 2018-11 on its required effective date of January 1, 2019 and elected both transition options mentioned above. ASU 2018-11 did not have a material impact on the Company’s Consolidated Financial Statements.

In December 2018, the FASB issued ASU No. 2018-20, “Narrow-Scope Improvements for Lessors.” This ASU (1) allows lessors to make an accounting policy election of presenting sales taxes and other similar taxes collected from lessees on a net basis, (2) requires a lessor to exclude lessor costs paid directly by a lessee to third parties on the lessor’s behalf and include lessor costs that are paid by the lessor and reimbursed by the lessee in the measurement of variable lease revenue and the associated expense, and (3) clarifies that when lessors allocate variable payments to lease and non-lease components they are required to follow the recognition guidance in the new leases standard for the lease component and other applicable guidance, such as the new revenue standard, for the non-lease component. The Company adopted ASU 2018-20 on its required effective date of January 1, 2019 and its adoption did not have a material impact on the Company’s Consolidated Financial Statements.

In March 2019, the FASB issued ASU No. 2019-01, “Leases: Codification Improvements.” This ASU (1) states that for lessors that are not manufacturers or dealers, the fair value of the underlying asset is its cost, less any volume or trade discounts, as long as there is not a significant amount of time between acquisition of the asset and lease commencement; (2) clarifies that lessors in the scope of ASC 942 (such as the Company) must classify principal payments received from sales-type and direct financing leases in investing activities in the statement of cash flows; and (3) clarifies the transition guidance related to certain interim disclosures provided in the year of adoption. To coincide with the adoption of ASU No. 2016-02, the Company elected to early adopt ASU 2019-01 on January 1, 2019. The adoption of this ASU did not have a material impact on the Company’s Consolidated Financial Statements.

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 became effective for us on January 1, 2019 and did not have a significant impact on the Company's Consolidated Financial Statements.

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 2018 Form 10-K for additional information related to previously issued accounting standards updates.

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. 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.