Business Segments (Policies)	12 Months Ended
Dec. 31, 2014
Segment Reporting [Abstract]
Segment Reporting Policy	Washington Trust segregates financial information in assessing its results among its Commercial Banking and Wealth Management Services operating segments. The amounts in the Corporate unit include activity not related to the segments. The methodologies and organizational hierarchies that define the business segments are periodically reviewed and revised. Results may be restated, when necessary, to reflect changes in organizational structure or allocation methodology. Any changes in estimates and allocations that may affect the reported results of any business segment will not affect the consolidated financial position or results of operations of Washington Trust as a whole. Management uses certain methodologies to allocate income and expenses to the business lines. A funds transfer pricing methodology is used to assign interest income and interest expense to each interest-earning asset and interest-bearing liability on a matched maturity funding basis. Certain indirect expenses are allocated to segments. These include support unit expenses such as technology and processing operations and other support functions. Commercial Banking The Commercial Banking segment includes commercial, residential and consumer lending activities; equity in losses of unconsolidated investments in real estate limited partnerships, mortgage banking, secondary market and loan servicing activities; deposit generation; merchant credit card services; cash management activities; and direct banking activities, which include the operation of ATMs, telephone and Internet banking services and customer support and sales. Wealth Management Services Wealth Management Services includes investment management; financial planning; personal trust services, including services as trustee, administrator, custodian and guardian; and estate settlement. Institutional trust services are also provided, including fiduciary services. Corporate Corporate includes the Treasury Unit, which is responsible for managing the wholesale investment portfolio and wholesale funding needs. It also includes income from bank-owned life insurance, net gain on sale of business line as well as administrative and executive expenses not allocated to the operating segments and the residual impact of methodology allocations such as funds transfer pricing offsets.

Washington Trust segregates financial information in assessing its results among its Commercial Banking and Wealth Management Services operating segments. The amounts in the Corporate unit include activity not related to the segments. The methodologies and organizational hierarchies that define the business segments are periodically reviewed and revised. Results may be restated, when necessary, to reflect changes in organizational structure or allocation methodology. Any changes in estimates and allocations that may affect the reported results of any business segment will not affect the consolidated financial position or results of operations of Washington Trust as a whole.

Management uses certain methodologies to allocate income and expenses to the business lines. A funds transfer pricing methodology is used to assign interest income and interest expense to each interest-earning asset and interest-bearing liability on a matched maturity funding basis. Certain indirect expenses are allocated to segments. These include support unit expenses such as technology and processing operations and other support functions.

Commercial Banking

The Commercial Banking segment includes commercial, residential and consumer lending activities; equity in losses of unconsolidated investments in real estate limited partnerships, mortgage banking, secondary market and loan servicing activities; deposit generation; merchant credit card services; cash management activities; and direct banking activities, which include the operation of ATMs, telephone and Internet banking services and customer support and sales.

Wealth Management Services

Wealth Management Services includes investment management; financial planning; personal trust services, including services as trustee, administrator, custodian and guardian; and estate settlement. Institutional trust services are also provided, including fiduciary services.

Corporate

Corporate includes the Treasury Unit, which is responsible for managing the wholesale investment portfolio and wholesale funding needs. It also includes income from bank-owned life insurance, net gain on sale of business line as well as administrative and executive expenses not allocated to the operating segments and the residual impact of methodology allocations such as funds transfer pricing offsets.