Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2022
Accounting Policies [Abstract]
Management's Use of Estimates	Management’s Use of Estimates The preparation of the consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (US GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of income and expenses during the reporting period. Management utilized estimates and assumptions in its evaluation of potential impairment of Arrow's right-of-use lease assets, goodwill and intangible assets. Our most significant estimate is the allowance for credit losses. Other estimates include the fair value of financial statements, evaluation of pension and other post-retirement liabilities, an analysis of a need for a valuation allowance for deferred tax assets and a reserve for unfunded loan commitments recorded as an other liability. Actual results could differ from those estimates. A material estimate that is particularly susceptible to significant change in the near term is the allowance for credit losses. In connection with the determination of the allowance for credit losses management obtains economic forecasts from reliable sources and appraisals for properties. The allowance for credit losses is management’s best estimate of the life of loan losses as of the balance sheet date. While management uses available information to recognize losses on loans, future adjustments to the allowance for credit losses may be necessary based on changes in economic conditions.
Allowance for Credit Losses	Allowance for Credit Losses – Loans - Accounting Standards Update (ASU) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (CECL) approach requires an estimate of the credit losses expected over the life of a loan (or pool of loans). It replaces the incurred loss approach’s threshold that required the recognition of a credit loss when it was probable that a loss event was incurred. The allowance for credit losses is a valuation account that is deducted from, or added to, the loans’ amortized cost basis to present the net, lifetime amount expected to be collected on the loans. Credit losses are charged off against the allowance when management believes a loan balance is confirmed to be uncollectible. Expected recoveries do not exceed the aggregate of amounts previously charged off and expected to be charged off. Management estimates the allowance using relevant available information from internal and external sources related to past events, current conditions, and a reasonable and supportable single economic forecast. Historical credit loss experience provides the basis for the estimation of expected credit losses. Arrow's historical loss experience was supplemented with peer information when there was insufficient loss data for Arrow. Peer selection was based on a review of institutions with comparable loss experience as well as loan yield, bank size, portfolio concentration and geography. Adjustments to historical loss information are made for differences in current loan-specific risk characteristics such as differences in credit concentrations, delinquency level, collateral values and underwriting standards as well as changes in economic conditions or other relevant factors. Management judgment is required at each point in the measurement process. Portfolio segment is defined as the level at which an entity develops and documents a systematic methodology to determine its allowance for credit losses. Upon adoption of CECL, management revised the manner in which loans were pooled for similar risk characteristics. Management developed portfolio segments for estimating loss based on type of borrower and collateral as follows: Commercial Loans Commercial Real Estate Loans Consumer Loans Residential Loans Further details related to loan portfolio segments is included in Note 4 Loans. Historical credit loss experience for both Arrow and segment-specific peers provides the basis for the estimation of expected credit losses. Arrow utilized regression analyses of peer data, of which Arrow is included, where observed credit losses and selected economic factors were utilized to determine suitable loss drivers for modeling lifetime probability of default (PD) rates. Arrow uses the discounted cash flow (DCF) method to estimate expected credit losses for the commercial, commercial real estate, and residential segments. For each of these loan segments, Arrow generates cash flow projections at the instrument level wherein payment expectations are adjusted for estimated prepayment speed, curtailments, time to recovery, PD, and segment-specific loss given default (LGD) risk factors. The modeling of expected prepayment speeds, curtailment rates, and time to recovery are based on historical internal data and adjusted, if necessary, based on the reasonable and supportable forecast of economic conditions. For the loan segments utilizing the DCF method, (commercial, commercial real estate, and residential) management utilizes externally developed economic forecast of the following economic factors as loss drivers: national unemployment, gross domestic product and home price index (HPI). The economic forecast is applied over a reasonable and supportable forecast period. Arrow utilizes a six quarter reasonable and supportable forecast period with an eight quarter reversion to the historic mean on a straight-line basis. The combination of adjustments for credit expectations (default and loss) and timing expectations (prepayment, curtailment, and time to recovery) produces an expected cash flow stream at the instrument level. Instrument effective yield is calculated, net of the impacts of prepayment assumptions, and the instrument expected cash flows are then discounted at that effective yield to produce an instrument-level net present value of expected cash flows (NPV). An allowance for credit loss is established for the difference between the instrument’s NPV and amortized cost basis. The contractual term excludes expected extensions, renewals, and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a troubled debt restructuring (TDR) will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by Arrow. Arrow uses the vintage analysis method to estimate expected credit losses for the consumer loan segment. The vintage method was selected since the loans within the consumer loan segment are homogeneous, not just by risk characteristic, but by loan structure. Under the vintage analysis method, a loss rate is calculated based on the quarterly net charge-offs to the outstanding loan balance for each vintage year over the lookback period. Once this periodic loss rate is calculated for each quarter in the lookback period, the periodic rates are averaged into the loss rate. The loss rate is then applied to the outstanding loan balances based on the loan's vintage year. Arrow maintains, over the life of the loan, the loss curve by vintage year. If estimated losses computed by the vintage method need to be adjusted based on current conditions and the reasonable and supportable economic forecast, these adjustments would be incorporated over a six quarter reasonable and supportable forecast period, reverting to historical losses using a straight-line method over an eight quarter period. Based on current conditions and the reasonable and supportable economic forecast, no adjustment to the loss rate for each vintage is currently required. The vintage and DCF models also consider the need to qualitatively adjust expected loss estimates for information not already captured in the quantitative loss estimation process. Qualitative considerations include limitations inherent in the quantitative model; trends experienced in nonperforming and delinquent loans; changes in value of underlying collateral; changes in lending policies and procedures; nature and composition of loans; portfolio concentrations that may affect loss experience across one or more components or the portfolio; the experience, ability and depth of lending management and staff; Arrow's credit review system; and the effect of external factors such as competition, legal and regulatory requirements. These qualitative factor adjustments may increase or decrease Arrow's estimate of expected credit losses so that the allowance for credit loss is reflective of the estimate of lifetime losses that exist in the loan portfolio at the balance sheet date. All loans not included in the vintage analysis method that exceed $250,000 which are on nonaccrual, are evaluated on an individual basis. For collateral dependent financial assets where Arrow has determined that foreclosure of the collateral is probable, or where the borrower is experiencing financial difficulty and Arrow expects repayment of the financial asset to be provided substantially through the operation or sale of the collateral, Arrow has elected a practical expedient to measure the allowance for credit loss as the difference between the fair value of the collateral less cost to sell, and the amortized cost basis of the asset as of the measurement date. In the event where the repayment of a collateral dependent financial asset is expected to be provided substantially through the operating of the collateral, Arrow will use fair value of the collateral at the reporting date when recording the net carrying amount of the asset and determining the allowance for credit losses. When repayment is expected to be from the sale of the collateral, expected credit losses are calculated as the amount by which the amortized cost basis of the financial asset exceeds the fair value of the underlying collateral less estimated cost to sell. The allowance for credit losses may be zero if the fair value of the collateral at the measurement date exceeds the amortized cost basis of the financial asset. Except as set forth below, a loan that has been modified or renewed is considered a TDR when two conditions are met: •The borrower is experiencing financial difficulty, and •Concessions are made for the borrower's benefit that would not otherwise be considered for a borrower or transaction with similar credit risk characteristics. Arrow's allowance for credit losses reflects all effects of a TDR when an individual asset is specifically identified as a reasonably expected TDR. Arrow has determined that a TDR is reasonably expected no later than the point it is determined that modification is the best course of action and it is at least reasonably possible that the troubled borrower will accept some form of concession to avoid a default. Reasonably expected TDRs and executed non-performing TDRs are evaluated individually to determine the required allowance for credit losses. TDRs performing in accordance with their modified contractual terms for a reasonable period of time may be included in Arrow's existing pools based on the underlying risk characteristics of the loan to measure the allowance for credit losses. Estimated Credit Losses on Off-Balance Sheet Credit Exposures Recognized as Other Liabilities - Arrow estimates expected credit losses over the contractual period in which Arrow has exposure to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by Arrow. The allowance for credit losses on off-balance sheet credit exposures recognized in other liabilities, is adjusted as an expense in other noninterest expense. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over their estimated lives. Estimating credit losses on unfunded commitments requires the Bank to consider the following categories of off-balance sheet credit exposure: unfunded commitments to extend credit, unfunded lines of credit, and standby letters of credit. Each of these unfunded commitments is then analyzed for a probability of funding to calculate a probable funding amount. The life of loan loss factor by related portfolio segment from the loan allowance for credit loss calculation is then applied to the probable funding amount to calculate the estimated credit losses on off-balance sheet credit exposures recognized as other liabilities. Accrued Interest Receivable - Upon adoption of CECL on January 1, 2021, Arrow made the following elections regarding accrued interest receivable: (1) presented accrued interest receivable balances separately within the other assets balance sheet line item; (2) excluded interest receivable that is included in amortized cost of financing receivables from related disclosures requirements and (3) continued Arrow's policy to write off accrued interest receivable by reversing interest income. For loans, write off typically occurs upon becoming over 90 to 120 days past due and therefore the amount of such write offs are immaterial. Historically, Arrow has not experienced uncollectible accrued interest receivable on investment securities. Allowance for Credit Losses – Held to Maturity (HTM) Debt Securities - Arrow's HTM debt securities are also required to utilize the CECL approach to estimate expected credit losses. Management measures expected credit losses on HTM debt securities on a collective basis by major security types that share similar risk characteristics, such as financial asset type and collateral type adjusted for current conditions and reasonable and supportable forecasts. Management classifies the HTM portfolio into the following major security types: U.S. government agency or U.S. government sponsored mortgage-backed and collateralized mortgage obligations securities, and state and municipal debt securities. The mortgage-backed and collateralized mortgage obligations HTM securities are issued by U.S. government entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government as to timely repayment of principal and interest, are highly rated by major rating agencies, and have a long history of no credit losses. Therefore, Arrow did not record a credit loss for these securities. State and municipal bonds carry an investment grade from an accredited ratings agency, primarily with an investment grade rating. In addition, Arrow has a limited amount of New York state local municipal bonds that are not rated. The estimate of expected credit losses on the HTM portfolio is based on the expected cash flows of each individual CUSIP over its contractual life and utilized a municipal loss forecast model for determining PD and LGD rates. Management may exercise discretion to make adjustments based on environmental factors. A calculated expected credit loss for individual securities was determined using the PD and LGD rates. Arrow determined that the expected credit loss on its municipal bond portfolio was de minimis, and therefore, an allowance for credit losses was not recorded. Allowance for Credit Losses – Available for Sale (AFS) Debt Securities - The impairment model for AFS debt securities differs from the CECL approach utilized by HTM debt securities since AFS debt securities are measured at fair value rather than amortized cost. For AFS debt securities in an unrealized loss position, the Bank first assesses whether it intends to sell, or it is more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For AFS debt securities that do not meet the aforementioned criteria, in making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, adverse conditions specifically related to the security, failure of the issuer of the debt security to make scheduled interest or principal payments, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. The cash flows are estimated using information relevant to the collectability of the security, including information about past events, current conditions and reasonable and supportable forecasts. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income. Investments in Federal Reserve Bank and Federal Home Loan Bank (FHLB) stock are required for membership in those organizations and are carried at cost since there is no market value available. The FHLB New York continues to pay dividends and repurchase stock. As such, the Company has not recognized any impairment on its holdings of Federal Reserve Bank and FHLB stock.

Allowance for Credit Losses – Loans - Accounting Standards Update (ASU) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (CECL) approach requires an estimate of the credit losses expected over the life of a loan (or pool of loans). It replaces the incurred loss approach’s threshold that required the recognition of a credit loss when it was probable that a loss event was incurred. The allowance for credit losses is a valuation account that is deducted from, or added to, the loans’ amortized cost basis to present the net, lifetime amount expected to be collected on the loans. Credit losses are charged off against the allowance when management believes a loan balance is confirmed to be uncollectible. Expected recoveries do not exceed the aggregate of amounts previously charged off and expected to be charged off.

Management estimates the allowance using relevant available information from internal and external sources related to past events, current conditions, and a reasonable and supportable single economic forecast. Historical credit loss experience provides the basis for the estimation of expected credit losses. Arrow's historical loss experience was supplemented with peer information when there was insufficient loss data for Arrow. Peer selection was based on a review of institutions with comparable loss experience as well as loan yield, bank size, portfolio concentration and geography. Adjustments to historical loss information are made for differences in current loan-specific risk characteristics such as differences in credit concentrations, delinquency level, collateral values and underwriting standards as well as changes in economic conditions or other relevant factors. Management judgment is required at each point in the measurement process.

Portfolio segment is defined as the level at which an entity develops and documents a systematic methodology to determine its allowance for credit losses. Upon adoption of CECL, management revised the manner in which loans were pooled for similar risk characteristics. Management developed portfolio segments for estimating loss based on type of borrower and collateral as follows:

Historical credit loss experience for both Arrow and segment-specific peers provides the basis for the estimation of expected credit losses. Arrow utilized regression analyses of peer data, of which Arrow is included, where observed credit losses and selected economic factors were utilized to determine suitable loss drivers for modeling lifetime probability of default (PD) rates. Arrow uses the discounted cash flow (DCF) method to estimate expected credit losses for the commercial, commercial real estate, and residential segments. For each of these loan segments, Arrow generates cash flow projections at the instrument level wherein payment expectations are adjusted for estimated prepayment speed, curtailments, time to recovery, PD, and segment-specific loss given default (LGD) risk factors. The modeling of expected prepayment speeds, curtailment rates, and time to recovery are based on historical internal data and adjusted, if necessary, based on the reasonable and supportable forecast of economic conditions.

For the loan segments utilizing the DCF method, (commercial, commercial real estate, and residential) management utilizes externally developed economic forecast of the following economic factors as loss drivers: national unemployment, gross domestic product and home price index (HPI). The economic forecast is applied over a reasonable and supportable forecast period. Arrow

The combination of adjustments for credit expectations (default and loss) and timing expectations (prepayment, curtailment, and time to recovery) produces an expected cash flow stream at the instrument level. Instrument effective yield is calculated, net of the impacts of prepayment assumptions, and the instrument expected cash flows are then discounted at that effective yield to produce an instrument-level net present value of expected cash flows (NPV). An allowance for credit loss is established for the difference between the instrument’s NPV and amortized cost basis. The contractual term excludes expected extensions, renewals, and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a troubled debt restructuring (TDR) will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by Arrow.

Arrow uses the vintage analysis method to estimate expected credit losses for the consumer loan segment. The vintage method was selected since the loans within the consumer loan segment are homogeneous, not just by risk characteristic, but by loan structure. Under the vintage analysis method, a loss rate is calculated based on the quarterly net charge-offs to the outstanding loan balance for each vintage year over the lookback period. Once this periodic loss rate is calculated for each quarter in the lookback period, the periodic rates are averaged into the loss rate. The loss rate is then applied to the outstanding loan balances based on the loan's vintage year. Arrow maintains, over the life of the loan, the loss curve by vintage year. If estimated losses computed by the vintage method need to be adjusted based on current conditions and the reasonable and supportable economic forecast, these adjustments would be incorporated over a six quarter reasonable and supportable forecast period, reverting to historical losses using a straight-line method over an eight quarter period. Based on current conditions and the reasonable and supportable economic forecast, no adjustment to the loss rate for each vintage is currently required.

The vintage and DCF models also consider the need to qualitatively adjust expected loss estimates for information not already captured in the quantitative loss estimation process. Qualitative considerations include limitations inherent in the quantitative model; trends experienced in nonperforming and delinquent loans; changes in value of underlying collateral; changes in lending policies and procedures; nature and composition of loans; portfolio concentrations that may affect loss experience across one or more components or the portfolio; the experience, ability and depth of lending management and staff; Arrow's credit review system; and the effect of external factors such as competition, legal and regulatory requirements. These qualitative factor adjustments may increase or decrease Arrow's estimate of expected credit losses so that the allowance for credit loss is reflective of the estimate of lifetime losses that exist in the loan portfolio at the balance sheet date.

All loans not included in the vintage analysis method that exceed $250,000 which are on nonaccrual, are evaluated on an individual basis. For collateral dependent financial assets where Arrow has determined that foreclosure of the collateral is probable, or where the borrower is experiencing financial difficulty and Arrow expects repayment of the financial asset to be provided substantially through the operation or sale of the collateral, Arrow has elected a practical expedient to measure the allowance for credit loss as the difference between the fair value of the collateral less cost to sell, and the amortized cost basis of the asset as of the measurement date. In the event where the repayment of a collateral dependent financial asset is expected to be provided substantially through the operating of the collateral, Arrow will use fair value of the collateral at the reporting date when recording the net carrying amount of the asset and determining the allowance for credit losses. When repayment is expected to be from the sale of the collateral, expected credit losses are calculated as the amount by which the amortized cost basis of the financial asset exceeds the fair value of the underlying collateral less estimated cost to sell. The allowance for credit losses may be zero if the fair value of the collateral at the measurement date exceeds the amortized cost basis of the financial asset.

Arrow's allowance for credit losses reflects all effects of a TDR when an individual asset is specifically identified as a reasonably expected TDR. Arrow has determined that a TDR is reasonably expected no later than the point it is determined that modification is the best course of action and it is at least reasonably possible that the troubled borrower will accept some form of concession to avoid a default. Reasonably expected TDRs and executed non-performing TDRs are evaluated individually to determine the required allowance for credit losses. TDRs performing in accordance with their modified contractual terms for a reasonable period of time may be included in Arrow's existing pools based on the underlying risk characteristics of the loan to measure the allowance for credit losses.

Estimated Credit Losses on Off-Balance Sheet Credit Exposures Recognized as Other Liabilities - Arrow estimates expected credit losses over the contractual period in which Arrow has exposure to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by Arrow. The allowance for credit losses on off-balance sheet credit exposures recognized in other liabilities, is adjusted as an expense in other noninterest expense. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over their estimated lives. Estimating credit losses on unfunded commitments requires the Bank to consider the following categories of off-balance sheet credit exposure: unfunded commitments to extend credit, unfunded lines of credit, and standby letters of credit. Each of these unfunded commitments is then analyzed for a probability of funding to calculate a probable funding amount. The life of loan loss factor by related portfolio segment from the loan allowance for credit loss calculation is then applied to the probable funding amount to calculate the estimated credit losses on off-balance sheet credit exposures recognized as other liabilities.

Accrued Interest Receivable - Upon adoption of CECL on January 1, 2021, Arrow made the following elections regarding accrued interest receivable: (1) presented accrued interest receivable balances separately within the other assets balance sheet line item; (2) excluded interest receivable that is included in amortized cost of financing receivables from related disclosures requirements and (3) continued Arrow's policy to write off accrued interest receivable by reversing interest income. For loans, write off typically occurs upon

Allowance for Credit Losses – Held to Maturity (HTM) Debt Securities - Arrow's HTM debt securities are also required to utilize the CECL approach to estimate expected credit losses. Management measures expected credit losses on HTM debt securities on a collective basis by major security types that share similar risk characteristics, such as financial asset type and collateral type adjusted for current conditions and reasonable and supportable forecasts. Management classifies the HTM portfolio into the following major security types: U.S. government agency or U.S. government sponsored mortgage-backed and collateralized mortgage obligations securities, and state and municipal debt securities.

The mortgage-backed and collateralized mortgage obligations HTM securities are issued by U.S. government entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government as to timely repayment of principal and interest, are highly rated by major rating agencies, and have a long history of no credit losses. Therefore, Arrow did not record a credit loss for these securities.

State and municipal bonds carry an investment grade from an accredited ratings agency, primarily with an investment grade rating. In addition, Arrow has a limited amount of New York state local municipal bonds that are not rated. The estimate of expected credit losses on the HTM portfolio is based on the expected cash flows of each individual CUSIP over its contractual life and utilized a municipal loss forecast model for determining PD and LGD rates. Management may exercise discretion to make adjustments based on environmental factors. A calculated expected credit loss for individual securities was determined using the PD and LGD rates. Arrow determined that the expected credit loss on its municipal bond portfolio was de minimis, and therefore, an allowance for credit losses was not recorded.

Allowance for Credit Losses – Available for Sale (AFS) Debt Securities - The impairment model for AFS debt securities differs from the CECL approach utilized by HTM debt securities since AFS debt securities are measured at fair value rather than amortized cost. For AFS debt securities in an unrealized loss position, the Bank first assesses whether it intends to sell, or it is more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For AFS debt securities that do not meet the aforementioned criteria, in making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, adverse conditions specifically related to the security, failure of the issuer of the debt security to make scheduled interest or principal payments, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. The cash flows are estimated using information relevant to the collectability of the security, including information about past events, current conditions and reasonable and supportable forecasts. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income.

Investments in Federal Reserve Bank and Federal Home Loan Bank (FHLB) stock are required for membership in those organizations and are carried at cost since there is no market value available. The FHLB New York continues to pay dividends and repurchase stock. As such, the Company has not recognized any impairment on its holdings of Federal Reserve Bank and FHLB stock.