Accounting Policies	9 Months Ended
Sep. 30, 2017
Accounting Policies [Abstract]
Accounting Policies	ACCOUNTING POLICIES In the opinion of the management of Arrow Financial Corporation (Arrow), the accompanying unaudited consolidated interim financial statements contain all of the adjustments necessary to present fairly the financial position as of September 30, 2017, December 31, 2016 and September 30, 2016; the results of operations for the three- and nine-month periods ended September 30, 2017 and 2016; the consolidated statements of comprehensive income for the three- and nine-month periods ended September 30, 2017 and 2016; the changes in stockholders' equity for the nine-month periods ended September 30, 2017 and 2016; and the cash flows for the nine-month periods ended September 30, 2017 and 2016. All such adjustments are of a normal recurring nature. Certain prior period amounts have been reclassified to conform to the current presentation, including a new requirement to present time deposits with balances greater than $250,000 which were previously presented as balances of $100,000 or greater. The preparation of financial statements requires the use of management estimates. The unaudited consolidated interim financial statements should be read in conjunction with the audited annual consolidated financial statements of Arrow for the year ended December 31, 2016, included in Arrow's 2016 Form 10-K. New Accounting Standards Updates (ASU): Effective January 1, 2017, Arrow adopted FASB accounting standard ASU 2016-09 "Improvements to Employee Share-Based Payment Accounting," which makes several revisions to equity compensation accounting. Under the new guidance all excess tax benefits and deficiencies that occur when an award is exercised or expires are recognized in income tax expense as discrete period items. Previously, these transactions were typically recorded directly within equity. Excess tax benefits are also recognized at the time an award is exercised compared to the previous requirement to delay recognition until the deduction reduces taxes payable. All tax related cash flows recognized on stock-based compensation expense are classified as an operating activity in our consolidated statements of cash flows on a prospective basis. Accordingly, prior periods have not been adjusted. ASU 2016-09 also provides an accounting policy election to recognize forfeitures of awards as they occur when estimating stock-based compensation expense rather than the previous requirement to estimate forfeitures from inception. Further, ASU 2016-09 permits employers to use a net-settlement feature to withhold taxes on equity compensation awards up to the maximum statutory tax rate without affecting the equity classification of the award. Under previous guidance, withholding of equity awards in excess of the minimum statutory requirement resulted in liability classification for the entire award. The related cash remittance by the employer for employee taxes is treated as a financing activity in the statement of cash flows. The annual effect of the 2017 tax provision will primarily depend upon the share price of Arrow common stock which affects the probability of exercise of certain stock options and the magnitude of windfalls upon exercise. Income tax benefits from stock options exercised in the period reduced our effective tax rate for the nine months ended September 30, 2017, which resulted in an increase in earnings of approximately $112 thousand, representing earnings per share of less than $0.01. In addition, during 2017, through the date of this report, the FASB issued 13 accounting standards updates. Some of the standards listed below did not have an immediate impact on Arrow, but could in the future. ASU 2014-09 - Revenue from Contracts with Customers will change revenue recognition guidance under GAAP and is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects consideration to which the entity expects to be entitled in exchange for those goods and services. The ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. 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. Initially, ASU 2014-09 was effective for Arrow on January 1, 2017; however, in August 2015, the FASB issued ASU No. 2015-14 - Revenue from Contracts with Customers - Deferral of the Effective Date, which deferred the effective date to January 1, 2018. Early adoption is not permitted. In addition, the FASB has begun to issue targeted updates to clarify specific implementation issues of ASU 2014-09. These updates include ASU No. 2016-08 - Principal versus Agent Considerations (Reporting Revenue Gross versus Net), ASU No. 2016-10 - Identifying Performance Obligations and Licensing, ASU No. 2016-12 - Narrow-Scope Improvements and Practical Expedients, and ASU No. 2016-20 - Technical Corrections and Improvements to Top 606 - Revenue from Contract with Customers. We are currently in the process of identifying any required changes to our revenue recognition policies. We do not expect that the adoption of this change in accounting for revenue will have a material impact on our financial position or the results of operations in periods subsequent to its adoption. ASU 2016-01 "Recognition and Measurement of Financial Assets and Financial Liabilities" will significantly change the income statement impact of equity investments. For Arrow, the standard is effective for the first quarter of 2018, and will require that equity investments be measured at fair value, with changes in fair value measured in net income. As of September 30, 2017, we hold $1.5 million of fair value in equity investments and we do not expect that the adoption of this change in accounting for equity investments will have a material impact on our financial position or the results of operations in periods subsequent to its adoption. ASU 2016-02 "Leases" will require the recognition of operating leases. For Arrow, the standard becomes effective in the first quarter of 2019. We do not expect that the adoption of this change in accounting for operating leases will have a material impact on our financial position or the results of operations in periods subsequent to its adoption. As of September 30, 2017, we have less than $2.6 million in minimum lease payments for existing operating leases of branch and insurance locations with varying expiration dates from 2017 to 2031. ASU 2016-13 "Financial Instruments - Credit Losses" will change the way we and other financial entities recognize losses on assets measured at amortized costs and change the method for recognizing credit losses on securities available-for-sale. Currently, loan losses are recognized using an "incurred loss" methodology. Under ASU 2016-13, the methodology will change to a current expected loss over the life of the loan. Currently, credit losses on available-for-sale securities reduce the carrying value of the instrument and cannot be reversed. Under ASU 2016-13, the amount of the credit loss is carried as a valuation allowance and can be reversed. For Arrow, the standard is effective for the first quarter of 2020 and early adoption is allowed in 2019. The Company is currently evaluating the impact of the pending adoption of the ASU on its consolidated financial statements. The initial adjustment will not be reported in earnings, but as the cumulative effect of a change in accounting principle. At this time we have not calculated the estimated impact that this Update will have on our Allowance for Loan Losses, however, we anticipate it will have a significant impact on the methodology process we utilize to calculate the allowance. ASU 2017-01 "Business Combinations" defines when a set of assets and activities constitutes a business for the purposes of determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. Currently, the three elements required to be present in a business are inputs, processes, and outputs. The amendments in this Update allow for a business to consist of inputs, processes, and the ability to create output. For Arrow, the standard becomes effective in the first quarter of 2018. This Update will likely have no effect on our accounting for acquisitions and dispositions of businesses. ASU 2017-04 "Intangibles-Goodwill and Other" changes the procedures for evaluating impairment of goodwill. Prior to this Update, entities were required to perform procedures to determine the fair value of the underlying assets and liabilities following the guidance for determining the fair value of assets and liabilities in a business combination. This additional step to impairment testing has been eliminated. Under the amendments in this Update, entities should perform goodwill impairment testing by comparing the fair value of a reporting unit to its carrying value. This amendment should reduce the cost and complexity of evaluating goodwill for impairment. For Arrow, the standard becomes effective in the first quarter of 2019, however, early adoption is permitted. This amendment will not affect our assessment of goodwill impairment since we currently perform the analysis of comparing carrying value to fair value of our reporting units that have goodwill and we have not had to perform a Step 2 Impairment Test to date. ASU 2017-07 "Compensation-Retirement Benefits" improves the presentation of net periodic pension cost and net periodic post-retirement benefit cost by requiring that an employer disaggregate the service cost component from the other components of net benefit cost. The amendments also provide explicit guidance on how to present the service cost component and the other components of net benefit cost in the income statement and allow only the service cost component of net benefit cost to be eligible for capitalization. For Arrow, the standard becomes effective in the first quarter of 2018, however, early adoption is permitted. We do not expect that the adoption of this change in accounting for pension costs will have a material impact on our financial position or the results of operations in periods subsequent to its adoption. ASU 2017-08 "Receivables-Nonrefundable Fees and Other Costs" amends the amortization period for certain purchased callable debt securities held at a premium. This shortens the amortization period for the premium to the earliest call date. Under current generally accepted accounting principles (GAAP), entities generally amortize the premium as an adjustment of yield over the contractual life of the instrument. For Arrow, the standard becomes effective in the first quarter of 2019, however, early adoption is permitted as early as the first quarter of 2017. We do not expect that the adoption of this change in accounting for certain callable debt securities will have a material impact on our financial position or the results of operations in periods subsequent to its adoption. ASU 2017-09 "Compensation-Stock Compensation" provides guidance about which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The guidance highlights the requirements for applying modification accounting and the exception criteria relating to changes in share-based payment terms. For Arrow, the standard becomes effective in the first quarter of 2018, however, early adoption is permitted as early as the third quarter of 2017. We do not expect that the adoption of this change in accounting for share-based payment awards will have a material impact on our financial position or the results of operations in periods subsequent to its adoption.

ACCOUNTING POLICIES

In the opinion of the management of Arrow Financial Corporation (Arrow), the accompanying unaudited consolidated interim financial statements contain all of the adjustments necessary to present fairly the financial position as of September 30, 2017, December 31, 2016 and September 30, 2016; the results of operations for the three- and nine-month periods ended September 30, 2017 and 2016; the consolidated statements of comprehensive income for the three- and nine-month periods ended September 30, 2017 and 2016; the changes in stockholders' equity for the nine-month periods ended September 30, 2017 and 2016; and the cash flows for the nine-month periods ended September 30, 2017 and 2016. All such adjustments are of a normal recurring nature. Certain prior period amounts have been reclassified to conform to the current presentation, including a new requirement to present time deposits with balances greater than $250,000 which were previously presented as balances of $100,000 or greater. The preparation of financial statements requires the use of management estimates. The unaudited consolidated interim financial statements should be read in conjunction with the audited annual consolidated financial statements of Arrow for the year ended December 31, 2016, included in Arrow's 2016 Form 10-K.

New Accounting Standards Updates (ASU): Effective January 1, 2017, Arrow adopted FASB accounting standard ASU 2016-09 "Improvements to Employee Share-Based Payment Accounting," which makes several revisions to equity compensation accounting. Under the new guidance all excess tax benefits and deficiencies that occur when an award is exercised or expires are recognized in income tax expense as discrete period items. Previously, these transactions were typically recorded directly within equity. Excess tax benefits are also recognized at the time an award is exercised compared to the previous requirement to delay recognition until the deduction reduces taxes payable. All tax related cash flows recognized on stock-based compensation expense are classified as an operating activity in our consolidated statements of cash flows on a prospective basis. Accordingly, prior periods have not been adjusted. ASU 2016-09 also provides an accounting policy election to recognize forfeitures of awards as they occur when estimating stock-based compensation expense rather than the previous requirement to estimate forfeitures from inception. Further, ASU 2016-09 permits employers to use a net-settlement feature to withhold taxes on equity compensation awards up to the maximum statutory tax rate without affecting the equity classification of the award. Under previous guidance, withholding of equity awards in excess of the minimum statutory requirement resulted in liability classification for the entire award. The related cash remittance by the employer for employee taxes is treated as a financing activity in the statement of cash flows.

The annual effect of the 2017 tax provision will primarily depend upon the share price of Arrow common stock which affects the probability of exercise of certain stock options and the magnitude of windfalls upon exercise. Income tax benefits from stock options exercised in the period reduced our effective tax rate for the nine months ended September 30, 2017, which resulted in an increase in earnings of approximately $112 thousand, representing earnings per share of less than $0.01.

In addition, during 2017, through the date of this report, the FASB issued 13 accounting standards updates. Some of the standards listed below did not have an immediate impact on Arrow, but could in the future.

ASU 2014-09 - Revenue from Contracts with Customers will change revenue recognition guidance under GAAP and is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects consideration to which the entity expects to be entitled in exchange for those goods and services. The ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. 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. Initially, ASU 2014-09 was effective for Arrow on January 1, 2017; however, in August 2015, the FASB issued ASU No. 2015-14 - Revenue from Contracts with Customers - Deferral of the Effective Date, which deferred the effective date to January 1, 2018. Early adoption is not permitted. In addition, the FASB has begun to issue targeted updates to clarify specific implementation issues of ASU 2014-09. These updates include ASU No. 2016-08 - Principal versus Agent Considerations (Reporting Revenue Gross versus Net), ASU No. 2016-10 - Identifying Performance Obligations and Licensing, ASU No. 2016-12 - Narrow-Scope Improvements and Practical Expedients, and ASU No. 2016-20 - Technical Corrections and Improvements to Top 606 - Revenue from Contract with Customers. We are currently in the process of identifying any required changes to our revenue recognition policies. We do not expect that the adoption of this change in accounting for revenue will have a material impact on our financial position or the results of operations in periods subsequent to its adoption.

ASU 2016-01 "Recognition and Measurement of Financial Assets and Financial Liabilities" will significantly change the income statement impact of equity investments. For Arrow, the standard is effective for the first quarter of 2018, and will require that equity investments be measured at fair value, with changes in fair value measured in net income. As of September 30, 2017, we hold $1.5 million of fair value in equity investments and we do not expect that the adoption of this change in accounting for equity investments will have a material impact on our financial position or the results of operations in periods subsequent to its adoption.

ASU 2016-02 "Leases" will require the recognition of operating leases. For Arrow, the standard becomes effective in the first quarter of 2019. We do not expect that the adoption of this change in accounting for operating leases will have a material impact on our financial position or the results of operations in periods subsequent to its adoption. As of September 30, 2017, we have less than $2.6 million in minimum lease payments for existing operating leases of branch and insurance locations with varying expiration dates from 2017 to 2031.

ASU 2016-13 "Financial Instruments - Credit Losses" will change the way we and other financial entities recognize losses on assets measured at amortized costs and change the method for recognizing credit losses on securities available-for-sale. Currently, loan losses are recognized using an "incurred loss" methodology. Under ASU 2016-13, the methodology will change to a current expected loss over the life of the loan. Currently, credit losses on available-for-sale securities reduce the carrying value of the instrument and cannot be reversed. Under ASU 2016-13, the amount of the credit loss is carried as a valuation allowance and can be reversed. For Arrow, the standard is effective for the first quarter of 2020 and early adoption is allowed in 2019. The Company is currently evaluating the impact of the pending adoption of the ASU on its consolidated financial statements. The initial adjustment will not be reported in earnings, but as the cumulative effect of a change in accounting principle. At this time we have not calculated the estimated impact that this Update will have on our Allowance for Loan Losses, however, we anticipate it will have a significant impact on the methodology process we utilize to calculate the allowance.

ASU 2017-01 "Business Combinations" defines when a set of assets and activities constitutes a business for the purposes of determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. Currently, the three elements required to be present in a business are inputs, processes, and outputs. The amendments in this Update allow for a business to consist of inputs, processes, and the ability to create output. For Arrow, the standard becomes effective in the first quarter of 2018. This Update will likely have no effect on our accounting for acquisitions and dispositions of businesses.

ASU 2017-04 "Intangibles-Goodwill and Other" changes the procedures for evaluating impairment of goodwill. Prior to this Update, entities were required to perform procedures to determine the fair value of the underlying assets and liabilities following the guidance for determining the fair value of assets and liabilities in a business combination. This additional step to impairment testing has been eliminated. Under the amendments in this Update, entities should perform goodwill impairment testing by comparing the fair value of a reporting unit to its carrying value. This amendment should reduce the cost and complexity of evaluating goodwill for impairment. For Arrow, the standard becomes effective in the first quarter of 2019, however, early adoption is permitted. This amendment will not affect our assessment of goodwill impairment since we currently perform the analysis of comparing carrying value to fair value of our reporting units that have goodwill and we have not had to perform a Step 2 Impairment Test to date.

ASU 2017-07 "Compensation-Retirement Benefits" improves the presentation of net periodic pension cost and net periodic post-retirement benefit cost by requiring that an employer disaggregate the service cost component from the other components of net benefit cost. The amendments also provide explicit guidance on how to present the service cost component and the other components of net benefit cost in the income statement and allow only the service cost component of net benefit cost to be eligible for capitalization. For Arrow, the standard becomes effective in the first quarter of 2018, however, early adoption is permitted. We do not expect that the adoption of this change in accounting for pension costs will have a material impact on our financial position or the results of operations in periods subsequent to its adoption.

ASU 2017-08 "Receivables-Nonrefundable Fees and Other Costs" amends the amortization period for certain purchased callable debt securities held at a premium. This shortens the amortization period for the premium to the earliest call date. Under current generally accepted accounting principles (GAAP), entities generally amortize the premium as an adjustment of yield over the contractual life of the instrument. For Arrow, the standard becomes effective in the first quarter of 2019, however, early adoption is permitted as early as the first quarter of 2017. We do not expect that the adoption of this change in accounting for certain callable debt securities will have a material impact on our financial position or the results of operations in periods subsequent to its adoption.

ASU 2017-09 "Compensation-Stock Compensation" provides guidance about which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The guidance highlights the requirements for applying modification accounting and the exception criteria relating to changes in share-based payment terms. For Arrow, the standard becomes effective in the first quarter of 2018, however, early adoption is permitted as early as the third quarter of 2017. We do not expect that the adoption of this change in accounting for share-based payment awards will have a material impact on our financial position or the results of operations in periods subsequent to its adoption.