Consolidation and Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018 shares	Mar. 31, 2019	Mar. 31, 2019 apartmentunits	Mar. 31, 2019 Property	Mar. 31, 2019 States	Mar. 31, 2019 Communities	Mar. 31, 2019 USD ($)	Mar. 31, 2019 shares	Mar. 31, 2019 ft²
Real Estate Properties [Line Items]
General Partners' Capital Account, Units Outstanding | shares		113,745,207							113,916,208
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	96.50%	96.50%
Number of owned or owned interests of apartment communities					303		303
Percentage Of Rental Revenue From Leasing Of Apartment Homes	93.00%
Percentage Of Reimbursable Revenue From Leasing Of Apartment Homes	6.00%
Percentage of Rental Revenue and Other Income From Non-leasing Activities	1.00%
Operating Lease, Liability								$ 33,557
Number of States in which Entity Operates | States						17
Minimum [Member]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests			80.00%
Maximum [Member]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests			100.00%
Development Properties [Member]
Real Estate Properties [Line Items]
Number of owned or owned interests of apartment communities | Communities							5
Number of units under development community | Property					1,090
Development Properties [Member] | Expected Costs [Member]
Real Estate Properties [Line Items]
Development and capital improvements in progress								230,500
Development Properties [Member] | Costs Incurred to Date [Member]
Real Estate Properties [Line Items]
Development and capital improvements in progress								59,500
Retail
Real Estate Properties [Line Items]
Number of owned or owned interests of apartment communities | Property					30
Square Footage of Real Estate Property | ft²										615,000
Commercial Real Estate [Member]
Real Estate Properties [Line Items]
Number of owned or owned interests of apartment communities | Property					4
Square Footage of Real Estate Property | ft²										260,000
Real Estate Technology Ventures, L.P. [Member]
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage			20.70%
Real Estate Investments, Joint Ventures								3,700
Real Estate Technology Ventures, L.P. [Member] | Limited Partner Capital Contribution, Future Obligation [Member]
Real Estate Properties [Line Items]
Real Estate Investments, Joint Ventures								13,600
Post River North [Member]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests			92.50%
Number of apartments included in a community | apartmentunits				359
Buildings, Improvements, and Other								69,800
Land								14,900
Accrued expenses and other liabilities								1,000
Post Massachusetts Avenue [Member]
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage			35.00%
Real Estate Investments, Joint Ventures								44,100
Phoenix Midtown [Member] [Domain]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests			80.00%
Buildings, Improvements, and Other								4,700
Land								9,400
Accrued expenses and other liabilities								700
Accounting Standards Update 2016-02 [Member]
Real Estate Properties [Line Items]
Operating Lease, Right-of-Use Asset								54,300
Operating Lease, Liability								$ 33,600
Operating Lease, Weighted Average Remaining Lease Term	33 years
Operating Lease, Weighted Average Discount Rate, Percent			4.40%