Fair Value Measurements (Policies)	9 Months Ended
Fair Value Measurements (Policies)	Sep. 30, 2012
Fair Value Disclosures [Abstract]
Fair Value Measurement Policy	Determination of Fair Value Fair values are based on the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When available, the Corporation uses quoted market prices to determine fair value. If quoted prices are not available, fair value is based upon valuation techniques such as matrix pricing or other models that use, where possible, current market-based or independently sourced market parameters, such as interest rates. If observable market-based inputs are not available, the Corporation uses unobservable inputs to determine appropriate valuation adjustments using methodologies applied consistently over time. The following is a description of valuation methodologies for assets and liabilities recorded at fair value, including the general classification of such assets and liabilities pursuant to the valuation hierarchy. Items Measured at Fair Value on a Recurring Basis Securities Securities available for sale are recorded at fair value on a recurring basis. When available, the Corporation uses quoted market prices to determine the fair value of securities; such items are classified as Level 1. This category includes exchange-traded equity securities. Level 2 securities include debt securities with quoted prices, which are traded less frequently than exchange-traded instruments, whose value is determined using matrix pricing with inputs that are observable in the market or can be derived principally from or corroborated by observable market data. This category generally includes obligations of U.S. government-sponsored enterprises, mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises, municipal bonds, trust preferred securities and corporate bonds. In certain cases where there is limited activity or less transparency around inputs to the valuation, securities may be classified as Level 3. As of September 30, 2012 and December 31, 2011, Level 3 securities were comprised of two pooled trust preferred debt securities, in the form of collateralized debt obligations, which were not actively traded. As of September 30, 2012 and December 31, 2011, the Corporation concluded that the low level of activity for its Level 3 pooled trust preferred debt securities continued to indicate that quoted market prices are not indicative of fair value. The Corporation obtained valuations including broker quotes and cash flow scenario analyses prepared by a third party valuation consultant. The fair values were assigned a weighting that was dependent upon the methods used to calculate the prices. The cash flow scenarios (Level 3) were given substantially more weight than the broker quotes (Level 2) as management believed that the broker quotes reflected highly limited sales evidenced by an inactive market. The cash flow scenarios were prepared using discounted cash flow methodologies based on detailed cash flow and credit analysis of the pooled securities. The weighting was then used to determine an overall fair value of the securities. Management believes that this approach is most representative of fair value for these particular securities in current market conditions. Our internal review procedures have also confirmed that the fair values provided by the aforementioned third party valuation sources utilized by the Corporation are consistent with GAAP. Our fair values assumed liquidation in an orderly market and not under distressed circumstances. Due to the continued market illiquidity and credit risk for securities in the financial sector, the fair value of these securities is highly sensitive to assumption changes and market volatility. Mortgage Loans Held for Sale Effective July 1, 2011, Washington Trust elected to carry newly originated closed residential real estate mortgage loans held for sale at fair value pursuant to ASC 825, "Financial Instruments." Level 2 mortgage loans held for sale fair values are estimated based on what secondary markets are currently offering for loans with similar characteristics. In certain cases when quoted market prices are not available, fair value is determined by utilizing a discounted cash flow analysis and these assets are classified as Level 3. Any change in the valuation of mortgage loans held for sale is based upon the change in market interest rates between closing the loan and the measurement date and an immaterial portion attributable to changes in instrument-specific credit risk. Derivatives Interest rate swap contracts are traded in over-the-counter markets where quoted market prices are not readily available. Fair value measurements are determined using independent pricing models that utilize primarily market observable inputs, such as swap rates of different maturities and LIBOR rates and, accordingly, are classified as Level 2. Our internal review procedures have confirmed that the fair values determined with independent pricing models and utilized by the Corporation are consistent with GAAP. For purposes of potential valuation adjustments to its interest rate swap contracts, the Corporation evaluates the credit risk of its counterparties as well as that of the Corporation. Accordingly, Washington Trust considers factors such as the likelihood of default by the Corporation and its counterparties, its net exposures and remaining contractual life, among other factors, in determining if any fair value adjustments related to credit risk are required. Counterparty exposure is evaluated by netting positions that are subject to master netting agreements, as well as considering the amount of collateral securing the position. Washington Trust met the criteria for and effective January 1, 2012 elected to apply the accounting policy exception with respect to measuring counterparty credit risk for derivative transactions subject to master netting arrangements provided in ASU 2011-04. Electing this policy exception had no impact on financial statement presentation. Level 2 fair value measurements of forward loan commitments (interest rate lock commitments and commitments to sell fixed-rate residential mortgages) are estimated using the anticipated market price based on pricing indications provided from syndicate banks. In certain cases when quoted market prices are not available, fair value is determined by utilizing a discounted cash flow analysis and these assets are classified as Level 3. Items Measured at Fair Value on a Nonrecurring Basis Collateral Dependent Impaired Loans Collateral dependent loans that are deemed to be impaired are valued based upon the fair value of the underlying collateral less costs to sell. Such collateral primarily consists of real estate and, to a lesser extent, other business assets. Management may adjust appraised values to reflect estimated market value declines or apply other discounts to appraised values resulting from its knowledge of the property. Internal valuations are utilized to determine the fair value of other business assets. Collateral dependent impaired loans are categorized as Level 3. Loan Servicing Rights Loan servicing rights do not trade in an active market with readily observable prices. Accordingly, we determine the fair value of loan servicing rights using a valuation model that calculates the present value of the estimated future net servicing income. The model incorporates assumptions used in estimating future net servicing income, including estimates of prepayment speeds, discount rate, cost to service and contractual servicing fee income. Loan servicing rights are subject to fair value measurements on a nonrecurring basis. Fair value measurements of our loan servicing rights use significant unobservable inputs and, accordingly, are classified as Level 3. Property Acquired Through Foreclosure or Repossession Property acquired through foreclosure or repossession is adjusted to fair value less costs to sell upon transfer out of loans. Subsequently, it is carried at the lower of carrying value or fair value less costs to sell. Fair value is generally based upon appraised values of the collateral. Management adjusts appraised values to reflect estimated market value declines or apply other discounts to appraised values for unobservable factors resulting from its knowledge of the property, and such property is categorized as Level 3.
Fair Value Transfer Policy	It is the Corporation’s policy to review and reflect transfers between Levels as of the financial statement reporting date. During the three and nine months ended September 30, 2012, there were no transfers in and/or out of Level 1, 2 or 3. During the third quarter of 2011, after evaluating forward loan commitments consisting of interest rate lock commitments and commitments to sell fixed-rate residential mortgages, it was determined that significant inputs and significant value drivers were observable in active markets, and the Corporation therefore reclassified these derivatives from out of Level 3 into Level 2. There were no other transfers during the three and nine months ended September 30, 2011.
Fair Value of Financial Instruments Policy	Valuation of Other Financial Instruments The methodologies for estimating the fair value of financial instruments that are measured at fair value on a recurring or nonrecurring basis are discussed above. The methodologies for other financial instruments are discussed below. Loans Fair values are estimated for categories of loans with similar financial characteristics. Loans are segregated by type and are then further segmented into fixed-rate and adjustable rate interest terms to determine their fair value. The fair value of fixed-rate commercial and consumer loans is calculated by discounting scheduled cash flows through the estimated maturity of the loan using interest rates offered at September 30, 2012 and December 31, 2011 that reflect the credit and interest rate risk inherent in the loan. The estimate of maturity is based on the Corporation's historical repayment experience. For residential mortgages, fair value is estimated by using quoted market prices for sales of similar loans on the secondary market, adjusted for servicing costs. The fair value of floating rate commercial and consumer loans approximates carrying value. Fair value for impaired loans is estimated using a discounted cash flow method based upon the loan’s contractual effective interest rate, or at the loan’s observable market price, or if the loan is collateral dependent, at the fair value of the collateral less costs to sell. Loans are classified within Level 3 of the fair value hierarchy. Time Deposits The discounted values of cash flows using the rates currently offered for deposits of similar remaining maturities were used to estimate the fair value of time deposits. Time deposits are classified within Level 2 of the fair value hierarchy. Federal Home Loan Bank Advances Rates currently available to the Corporation for advances with similar terms and remaining maturities are used to estimate fair value of existing advances. FHLBB advances are categorized as Level 2. Junior Subordinated Debentures The fair value of the junior subordinated debentures is estimated using rates currently available to the Corporation for debentures with similar terms and maturities. Junior subordinated debentures are categorized as Level 2.