Business (Details)	Jun. 30, 2011
Property/Unit schedule
Wholly Owned Properties	397
Wholly Owned Units	111,539
Partially Owned Consolidated Properties	22
Partially Owned Consolidated Units	4,371
Military Housing Properties	2
Military Housing Units	4,850
Total Properties	421
Total Units	120,760
Business (Textuals) [Abstract]
EQR's Ownership percentage in ERPOP	95.60%
Properties owned	421
States in which properties owned are located	16
Units owned	120,760

Business.

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Total number of rental properties that represent military housing but are not consolidated by the Company.

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Total number of units associated with rental properties that represent military housing but are not consolidated by the Company

Total number of rental properties that are partially owned and consolidated by the Company.

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Total number of units associated with rental properties that are partially owned and consolidated by the Company.

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Schedule of properties and units.

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Total number of rental properties that are wholly owned and consolidated by the Company.

Total number of units associated with rental properties that are wholly owned and consolidated by the Company.

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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The number of real estate properties owned as of the balance sheet date.

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The number of states the entity operates in as of the balance sheet date.

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The number of units in a real estate property owned as of the balance sheet date.

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