Securities (Securities Pooled Trust Preferred Unrealized Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized cost of the first trust preferred security of pooled issuers on nonaccrual status	$ 0	[1],[2]	$ 2,772	[1],[2]
Trust Preferred Securities Pooled Issuers On Nonaccrual Status Fair Value First Security	0	[1]	613	[1]
Unrealized losses of the first trust preferred security of pooled issuers on nonaccrual status	0	[1]	(2,159)	[1]
Trust Preferred Securities Pooled Issuers on Nonaccrual Status Amortized Cost Second Security	1,264	[2],[3]	1,264	[2],[3]
Trust Preferred Securities Pooled Issuers On Nonaccrual Status Fair Value Second Security	404	[3]	230	[3]
Unrealized losses of the second trust preferred security of pooled issuers on nonaccrual status	(860)	[3]	(1,034)	[3]
Available for sale debt securities fair value	350,205
Available for sale securities unrealized losses	(5,972)		(9,119)
Current credit-related impairment losses of the first trust preferred security on nonaccrual status	2,772
Total credit-related impairment losses of the first trust preferred security of pooled issuers on nonaccrual status	2,096
Total credit-related impairment losses of the second trust preferred security of pooled issuers on nonaccrual status	1,229
Trust preferred securities: Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale debt securities amortized cost	1,264	[2]	4,036	[2]
Available for sale debt securities fair value	404		843
Available for sale securities unrealized losses	$ (860)		$ (3,193)

[1] In the first quarter of 2013, Washington Trust recognized an other-than-temporary impairment charge of $2.8 million on the Tropic CDO 1, tranche A4L (“Tropic”). On March 22, 2013, the trustee for the Tropic security issued a notice that a liquidation of the CDO entity, Tropic CDO I, Ltd., will take place at the direction of holders of the CDO tranches that are senior to certain subordinate tranches, of which Washington Trust is a note holder. The estimated proceeds from the liquidation event are expected to be insufficient to satisfy the amount owed to the note holders of the CDO's subordinate tranches. The Corporation had recognized other-than-temporary losses amounting to $2.1 million on this security in years prior to 2013; however, prior to the March 2013 announcement of the liquidation event, the expected future cash flows through the maturity of the CDO in the year 2033 were considered to be sufficient to recover the Corporation's remaining $2.8 million amortized cost. The first quarter impairment loss reduces the Corporation's carrying value in the holding to zero. The security had been classified in nonaccruing status with no interest recognition since 2009.

[2] Net of other-than-temporary impairment losses recognized in earnings.

[3] Washington Trust’s investment is subordinate to two senior tranche levels. Valuations of the pooled trust preferred holdings is dependent in part on cash flows from underlying issuers. Unexpected cash flow disruptions could have an adverse impact on the fair value and performance of this pooled trust preferred security. Management believes the unrealized losses on this pooled trust preferred security primarily reflects investor concerns about global economic growth and how it will affect the recent and potential future losses in the financial services industry and the possibility of further incremental deferrals of or defaults on interest payments on trust preferred debentures by financial institutions participating in these pools. These concerns have resulted in a substantial decrease in market liquidity and increased risk premiums for securities in this sector. Credit spreads for issuers in this sector have remained wide during recent months, causing prices for this security holding to remain at low levels.This security was placed on nonaccrual status in December 2008. The tranche instrument held by Washington Trust has been deferring interest payments since December 2008. The March 31, 2013 amortized cost was net of $1.2 million of credit-related impairment losses previously recognized in earnings reflective of payment deferrals and credit deterioration of the underlying collateral. As of March 31, 2013, this security had unrealized losses of $860 thousand and a below investment grade rating of “C” by Moody’s. Through the filing date of this report, there have been no additional rating changes on this security. This credit rating status has been considered by management in its assessment of the impairment status of this security. Based on information available through the filing date of this report, there have been no additional adverse changes in deferral or default status of the underlying issuer institutions. Based on cash flow forecasts for this security, management expects to recover the remaining amortized cost of this security. Furthermore, Washington Trust does not intend to sell this security and its is not more likely than not that Washington Trust will be required to sell this security before recovery of its cost basis, which may be at maturity. Therefore, management does not consider the unrealized losses on this security to be other-than-temporary at March 31, 2013.