Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2015
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	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, 2015, December 31, 2014 and September 30, 2014; the results of operations for the three-month and nine-month periods ended September 30, 2015 and 2014; the consolidated statements of comprehensive income for the three-month and nine-month periods ended September 30, 2015 and 2014; the changes in stockholders' equity for the nine-month periods ended September 30, 2015 and 2014; and the cash flows for the nine-month periods ended September 30, 2015 and 2014. All such adjustments are of a normal recurring nature. Certain prior period amounts have been reclassified to conform to the current presentation. 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, 2014, included in Arrow's 2014 Form 10-K. New Accounting Standards Updates (ASU): During 2015, through the date of this report, the FASB issued 16 accounting standards updates, The standards listed below did not have had an immediate impact on Arrow, but could in the future. ASU 2015-01 "Income Statement - Extraordinary and Unusual Items" eliminated the concept of extraordinary items. For Arrow, the standard is effective for the first quarter of 2016. ASU 2015-02 "Consolidation" changed the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. For Arrow, the standard is effective for the first quarter of 2016. ASU 2015-03 and ASU 2015-15 "Interest - Imputation of Interest" required debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability. There were no changes to the recognition and measurement of debt issuance costs. For Arrow, the standard is effective for the first quarter of 2016. ASU 2015-04 "Compensation-Retirement Benefits" provides several practical expedients for the measurement or, in certain circumstances, the remeasurement of defined benefit plan assets and obligations. Most of the practical expedients will not apply to Arrow, however, if used, an entity must disclose the accounting policy election and the date used to measure defined benefit plan assets and obligations. For Arrow, the standard is effective for the first quarter of 2016. ASU 2015-05 "Intangibles - Goodwill and Other - Internal use Software" provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. For Arrow, the standard is effective for the first quarter of 2016. ASU 2015-06 "Earnings Per Share" contains guidance that addresses master limited partnerships. For Arrow, the standard is effective for the first quarter of 2016. ASU 2015-07 "Fair Value Measurement" permits a reporting entity to measure the fair value of certain investments using the net asset value per share of the investment. For Arrow, the standard is effective for the first quarter of 2016. ASU 2015-08 "Business Combinations" amended various SEC paragraphs pursuant to SEC Staff Accounting Bulletin No. 115.

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, 2015, December 31, 2014 and September 30, 2014; the results of operations for the three-month and nine-month periods ended September 30, 2015 and 2014; the consolidated statements of comprehensive income for the three-month and nine-month periods ended September 30, 2015 and 2014; the changes in stockholders' equity for the nine-month periods ended September 30, 2015 and 2014; and the cash flows for the nine-month periods ended September 30, 2015 and 2014. All such adjustments are of a normal recurring nature. Certain prior period amounts have been reclassified to conform to the current presentation. 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, 2014, included in Arrow's 2014 Form 10-K.

New Accounting Standards Updates (ASU): During 2015, through the date of this report, the FASB issued 16 accounting standards updates, The standards listed below did not have had an immediate impact on Arrow, but could in the future.

ASU 2015-01 "Income Statement - Extraordinary and Unusual Items" eliminated the concept of extraordinary items. For Arrow, the standard is effective for the first quarter of 2016.

ASU 2015-02 "Consolidation" changed the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. For Arrow, the standard is effective for the first quarter of 2016.

ASU 2015-03 and ASU 2015-15 "Interest - Imputation of Interest" required debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability. There were no changes to the recognition and measurement of debt issuance costs. For Arrow, the standard is effective for the first quarter of 2016.

ASU 2015-04 "Compensation-Retirement Benefits" provides several practical expedients for the measurement or, in certain circumstances, the remeasurement of defined benefit plan assets and obligations. Most of the practical expedients will not apply to Arrow, however, if used, an entity must disclose the accounting policy election and the date used to measure defined benefit plan assets and obligations. For Arrow, the standard is effective for the first quarter of 2016.

ASU 2015-05 "Intangibles - Goodwill and Other - Internal use Software" provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. For Arrow, the standard is effective for the first quarter of 2016.

ASU 2015-06 "Earnings Per Share" contains guidance that addresses master limited partnerships. For Arrow, the standard is effective for the first quarter of 2016.

ASU 2015-07 "Fair Value Measurement" permits a reporting entity to measure the fair value of certain investments using the net asset value per share of the investment. For Arrow, the standard is effective for the first quarter of 2016.

ASU 2015-08 "Business Combinations" amended various SEC paragraphs pursuant to SEC Staff Accounting Bulletin No. 115.