Area of Real Estate Property Disposed

No definition available.

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- Definition

Disposal Group, Not Discontinued Operation, Percentage Of Equity Interests In Fee Simple Owner Sold

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Gain (Loss) on Sale of Properties, Release Of Escrow Deposits

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

This element represents the number of buildings sold or agreed to be sold by the entity.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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Period Type:	duration

- Definition

Number Of Real Estate Properties Sold

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The element represents the aggregate sales price excluding mortgage debt repayments and closing costs, of real estate properties sold or agreed to be sold by the entity.

+ References

No definition available.

+ Details

Name:	eqc_RealEstateAggregateSalesPrice
Namespace Prefix:	eqc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Escrow deposits related to property sales in noncash investing and financing activities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
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-URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4313-108586

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
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-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2443-110228

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Balance Type:	credit
Period Type:	duration

- Definition

Amount before tax of income (loss) from an individually significant component disposed of or held-for-sale including the portion attributable to the noncontrolling interest. Excludes discontinued operations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3A
-Subparagraph (a)(1)
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Data Type:	xbrli:monetaryItemType
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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Real Estate Properties - Summary of Properties Disposed (Details) $ in Thousands	1 Months Ended												12 Months Ended
	May 31, 2020 USD ($) ft² property building	Mar. 31, 2020 USD ($) ft² building property	Feb. 29, 2020 USD ($) ft² property building	Jun. 30, 2019 USD ($) ft² property building	Apr. 30, 2019 USD ($) ft² building property	Mar. 31, 2019 USD ($) ft² building property	Dec. 31, 2018 USD ($) ft² building property	Sep. 30, 2018 USD ($) ft² property building	Aug. 31, 2018 USD ($) ft² property building	May 31, 2018 USD ($) ft² building property	Mar. 31, 2018 USD ($) ft² property building	Feb. 28, 2018 USD ($) ft² property building	Dec. 31, 2020 USD ($) ft² property building	Dec. 31, 2019 USD ($) ft² building property	Dec. 31, 2018 USD ($) ft² building property
Real Estate Properties [Line Items]
Gain (Loss) on Sale													$ 446,744	$ 422,172	$ 251,417
Disposed of by Sale
Real Estate Properties [Line Items]
Number of Properties \| property													3	3	7
Number of Buildings \| building													4	6	9
Square Footage (in sqft) \| ft²													961,437	2,651,453	4,404,797
Gross Sales Price													$ 756,500	$ 812,100	$ 1,031,286
Gain (Loss) on Sale													444,768	420,152	251,458
Disposed of by Sale \| 109 Brookline Avenue
Real Estate Properties [Line Items]
Number of Properties \| property			1
Number of Buildings \| building			1
Square Footage (in sqft) \| ft²			285,556
Gross Sales Price			$ 270,000
Gain (Loss) on Sale			$ 225,190
Disposed of by Sale \| 333 108th Avenue NE
Real Estate Properties [Line Items]
Number of Properties \| property		1
Number of Buildings \| building		1
Square Footage (in sqft) \| ft²		435,406
Gross Sales Price		$ 401,500
Gain (Loss) on Sale		$ 194,662											194,700
Net income included in continued operations													193,400	14,200	12,800
Disposed of by Sale \| Georgetown-Green and Harris Buildings
Real Estate Properties [Line Items]
Number of Properties \| property	1
Number of Buildings \| building	2
Square Footage (in sqft) \| ft²	240,475
Gross Sales Price	$ 85,000
Gain (Loss) on Sale	$ 24,916
Disposed of by Sale \| 1735 Market Street
Real Estate Properties [Line Items]
Number of Properties \| property						1
Number of Buildings \| building						1
Square Footage (in sqft) \| ft²						1,286,936
Gross Sales Price						$ 451,600
Gain (Loss) on Sale						$ 192,985							193,000
Percentage of equity interests in fee simple owner sold						100.00%
Net income included in continued operations													100	197,500	8,500
Disposed of by Sale \| 600 108th Avenue NE
Real Estate Properties [Line Items]
Number of Properties \| property					1
Number of Buildings \| building					1
Square Footage (in sqft) \| ft²					254,510
Gross Sales Price					$ 195,000
Gain (Loss) on Sale					$ 149,009
Disposed of by Sale \| Research Park
Real Estate Properties [Line Items]
Number of Properties \| property				1
Number of Buildings \| building				4
Square Footage (in sqft) \| ft²				1,110,007
Gross Sales Price				$ 165,500
Gain (Loss) on Sale				$ 78,158
Escrow deposits related to property sales													2,000
Additional gain on sale of properties, release of escrow deposits													2,000
Disposed of by Sale \| 1600 Market Street
Real Estate Properties [Line Items]
Number of Properties \| property												1
Number of Buildings \| building												1
Square Footage (in sqft) \| ft²												825,968
Gross Sales Price												$ 160,000
Gain (Loss) on Sale												$ 54,599
Disposed of by Sale \| 600 West Chicago Avenue
Real Estate Properties [Line Items]
Number of Properties \| property												1
Number of Buildings \| building												2
Square Footage (in sqft) \| ft²												1,561,477
Gross Sales Price												$ 510,000
Gain (Loss) on Sale												$ 107,790
Net income included in continued operations													$ 300	$ 300	$ 110,600
Disposed of by Sale \| 5073, 5075, & 5085 S. Syracuse Street
Real Estate Properties [Line Items]
Number of Properties \| property											1
Number of Buildings \| building											1
Square Footage (in sqft) \| ft²											248,493
Gross Sales Price											$ 115,186
Gain (Loss) on Sale											$ 42,762
Disposed of by Sale \| 1601 Dry Creek Drive
Real Estate Properties [Line Items]
Number of Properties \| property										1
Number of Buildings \| building										1
Square Footage (in sqft) \| ft²										552,865
Gross Sales Price										$ 68,500
Gain (Loss) on Sale										$ 26,979
Disposed of by Sale \| 777 East Eisenhower Parkway
Real Estate Properties [Line Items]
Number of Properties \| property									1
Number of Buildings \| building									1
Square Footage (in sqft) \| ft²									290,530
Gross Sales Price									$ 29,500
Gain (Loss) on Sale									$ 5,308
Disposed of by Sale \| 8750 Bryn Mawr Avenue
Real Estate Properties [Line Items]
Number of Properties \| property								1
Number of Buildings \| building								2
Square Footage (in sqft) \| ft²								636,078
Gross Sales Price								$ 141,000
Gain (Loss) on Sale								$ 15,194
Disposed of by Sale \| 97 Newberry Road
Real Estate Properties [Line Items]
Number of Properties \| property							1
Number of Buildings \| building							1
Square Footage (in sqft) \| ft²							289,386
Gross Sales Price							$ 7,100
Gain (Loss) on Sale							$ (1,174)