Stock Based Compensation (Narrative) (Details) (USD $)	6 Months Ended
Jun. 30, 2011
New STIP [Member]
Percentage of cash portion pursuant to deferred compensation plan	80.00%
Percentage of deferred amounts in restricted cash	25.00%
Percentage of restricted shares subject to performance conditions	20.00%
New STIP [Member] \| Performance-Based Awards [Member]
Vesting period	three
New STIP [Member] \| Performance-Based Awards [Member] \| Cash [Member]
Percentage of awards earned	50.00%
New STIP [Member] \| Performance-Based Awards [Member] \| Restricted Share Units [Member]
Percentage of awards earned	50.00%
New STIP [Member] \| Service-Based Awards [Member]
Vesting period	three
New STIP [Member] \| Service-Based Awards [Member] \| Restricted Share Units [Member]
Percentage of awards earned	15.00%
New LTIP [Member]
Percentage of restricted shares subject to performance conditions	60.00%
Percentage of potential award depend upon market condition	40.00%
New LTIP [Member] \| Restricted Share Units [Member]
Percentage of awards earned	50.00%
Vesting period	one
New LTIP [Member] \| Unrestricted Share Units [Member]
Percentage of awards earned	50.00%
New LTIP [Member] \| Restricted Share Awards [Member]
Compensation expense recognized period	4
New LTIP [Member] \| Unrestricted Share Awards [Member]
Compensation expense recognized period	3
Prior LTIP [Member]
Vesting period	five
Compensation expense recognized period	6
Number of restricted shares subsequent to adoption of new share-based compensation plan	154,400
Remaining unvested restricted shares granted	0
Restricted shares granted during the period	0
Washington Real Estate Investment Trust 2007 Omnibus Long-Term Incentive Plan [Member]
Stock based plan, aggregate number of shares authorized	2,000,000
Stock based plan, period in force	10
Vest on December 31, 2011 [Member] \| Restricted Share Units [Member]
Total number of share units awarded	89,000
Vest on December 31, 2012 [Member] \| Restricted Share Units [Member]
Total number of share units awarded	65,400
Restricted And Unrestricted Shares [Member]
Total Fair value of vested shares	28,800
Shares vested	0
Remaining unvested restricted shares granted	10,822
Restricted shares granted during the period	10,822
Unamortized value of share units	300,000
Unamortized value of unvested share awards	295,200
Compensation cost of restricted shares	1,000,000
Weighted average period of recognition, unamortized value (months)	30
Options [Member]
Options outstanding	114,403
Exercise price, minimum	24.85
Exercise price, maximum	33.09
Weighted average exercise price, options outstanding	27.23
Weighted average remaining contractual term, options outstanding (years)	1.8
Aggregate intrinsic value of outstanding exercisable shares	600,000
Options exercised	31,582
Aggregate intrinsic value of options exercised	200,000
Restricted Share Units [Member]
Total Fair value of vested shares	247,100
Value of unvested restricted share units	5,000,000
Weighted average period of recognition, compensation cost (months)	28
Weighted average period of recognition, unamortized value (months)	30
Future expected expense expected to be awarded to non-officers	1,100,000
Restricted Share Awards [Member]
Weighted average period of recognition, unamortized value (months)	42
Unrestricted Share Awards [Member]
Weighted average period of recognition, unamortized value (months)	30

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

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Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph b(2)(a)
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-Name Statement of Financial Accounting Standard (FAS)
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The liabilities paid during the accounting period for equity-based compensation.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

The total fair value of equity-based awards for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of vested portions of options outstanding and currently exercisable under the option plan as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
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-Publisher FASB
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- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph 64
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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The weighted-average period remaining as of the balance sheet date until option expiration pertaining to the outstanding stock options for all option plans in the customized range of exercise prices, which may be expressed in a variety of ways (for example, years, months).

+ References

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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- Definition

Number of share options (or share units) exercised during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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-Name Accounting Standards Codification
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-Name Regulation S-X (SX)
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- Definition

Future Expected Expense with Performance Conditions Expected To Be Awarded

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- Definition

Number of Restricted Shares Subsequent to Adoption of New share-based Compensation Plan

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- Definition

Percentage Of Awards Earned

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Balance Type:	na
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- Definition

Percentage Of Cash Portion Related To Deferred Compensation Plan

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- Definition

Percentage Of Deferred Amounts In Restricted Cash

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- Definition

Percentage Of Potential Award Depend Upon Market Condition

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- Definition

Percentage Of Restricted Shares Subject To Performance Conditions

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Total Intrinsic Value

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- Definition

Stock Based Plan, Period in Force

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- Definition

Unamortized Value Of Share Units

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- Definition

Weighted Average Period Of Cost Recognition

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Weighted Average Period Of Unamortized Value Recognition

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