Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General Information	Basis of Presentation Washington Trust Bancorp, Inc. (the “Bancorp”) is a publicly-owned registered bank holding company that has elected to be a financial holding company. The Bancorp’s subsidiaries include The Washington Trust Company, of Westerly (the “Bank”), a Rhode Island chartered commercial bank founded in 1800, and Weston Securities Corporation (“WSC”). Through its subsidiaries, the Bancorp offers a complete product line of financial services, including commercial, residential and consumer lending, retail and commercial deposit products, and wealth management services through its offices in Rhode Island, eastern Massachusetts and Connecticut. The Unaudited Consolidated Financial Statements include the accounts of the Bancorp and its subsidiaries (collectively the “Corporation” or “Washington Trust”). All intercompany balances and transactions have been eliminated. The Bancorp also owns the common stock of two capital trusts, which have issued trust preferred securities. These capital trusts are variable interest entities in which the Bancorp is not the primary beneficiary and, therefore, are not consolidated. The capital trust’s only assets are junior subordinated debentures issued by the Bancorp, which were acquired by the capital trusts using the proceeds from the issuance of the trust preferred securities and common stock. The Bancorp’s equity interest in the capital trusts, classified in other assets, and the junior subordinated debentures are included in the Unaudited Consolidated Balance Sheets. Interest expense on the junior subordinated debentures is included in the Unaudited Consolidated Statements of Income. The accounting and reporting policies of the Corporation conform to accounting principles generally accepted in the United States of America (“GAAP”) and to general practices of the banking industry. In preparing the financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and revenues and expenses for the period. Actual results could differ from those estimates. The Unaudited Consolidated Financial Statements of the Corporation presented herein have been prepared pursuant to the rules of the Securities and Exchange Commission (“SEC”) for quarterly reports on Form 10-Q and do not include all of the information and note disclosures required by GAAP. In the opinion of management, all adjustments (consisting of normal recurring adjustments) and disclosures considered necessary for the fair presentation of the accompanying Unaudited Consolidated Financial Statements have been included. Interim results are not necessarily indicative of the results of the entire year. The accompanying Unaudited Consolidated Financial Statements should be read in conjunction with the Audited Consolidated Financial Statements and notes thereto included in the Annual Report on Form 10-K for the fiscal year ended December 31, 2019. Risks and Uncertainties The COVID-19 pandemic has caused an unprecedented disruption to the economy and the communities we serve. The U.S. government and regulatory agencies have taken several actions to provide support to the U.S. economy. Most notably, the Coronavirus Aid, Relief and Economic Security Act (the “CARES Act”), a $2 trillion stimulus bill, was signed into law on March 27, 2020. The goal of the CARES Act was to prevent a severe economic downturn through various measures, including direct financial aid to American families and economic stimulus to significantly impacted industry sectors. The CARES Act also included extensive emergency funding for hospitals and providers. In addition to the general impact of the COVID-19 pandemic, certain provisions of the CARES Act, as well as other recent legislative and regulatory relief efforts, could have a material impact on the Corporation’s operations. Also, the actions of the Board of Governors of the Federal Reserve System (the “FRB”) to combat the economic contraction caused by the COVID-19 pandemic, including the reduction of the target federal funds rate and quantitative easing programs, could, if prolonged, adversely affect the Corporation’s net interest income and margins, and profitability. Continued uncertainty regarding the severity and duration of the COVID-19 pandemic and related economic effects will continue to affect the accounting for credit losses. It also is possible that asset quality could worsen, expenses associated with collection efforts could increase and loan charge-offs could increase. Washington Trust is participating in the Small Business Administration's (“SBA’s”) Paycheck Protection Program (“PPP”), providing loans to small businesses negatively impacted by the COVID-19 pandemic. PPP loans are fully guaranteed by the U.S. government, if that should change, Washington Trust could be required to increase its allowance for credit losses through an additional provision for credit losses charged to earnings. PPP loans amounted to $216.8 million as of September 30, 2020. The extent to which the COVID-19 pandemic will continue to impact the Corporation’s business, results of operations, and financial condition, as well as regulatory capital and liquidity ratios, will depend on future developments, including the scope and duration of the pandemic and actions taken by governmental authorities and other third parties in response to the pandemic, as well as further actions the Corporation may take as may be required by government authorities or that the Corporation determines is in the best interests of its employees and customers. There is no certainty that such measures will be sufficient to mitigate the risks posed by the pandemic.