Schedule III Real Estate and Accumulated Depreciation (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) Contract
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Federal Income Tax Basis	$ 10,800,000,000
Encumbrance 1 | FNMA
Real Estate and Accumulated Depreciation [Line Items]
Secured credit facilities, amount available	80,000,000
Line of credit facility, amount outstanding	$ 80,000,000
Variable interest rate (percent)	1.80%
Encumbrance 1 | FNMA | Interest Rate Swap
Real Estate and Accumulated Depreciation [Line Items]
Number of Interest rate derivatives held (contracts) | Contract	1
Variable rate borrowings after interest rate swaps (percent)	4.50%
Encumbrance 1 | FNMA | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Derivative, Notional Amount	$ 25,000,000
Encumbrance 2 | Fixed Rate Debt | Loan [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	$ 125,200,000.0
Derivative cap interest rate (percent)	5.08%
Derivative termination date	Jun. 10, 2021
Furniture, fixtures and equipment
Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives (years)	5 years
Minimum | Land improvements and buildings
Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives (years)	8 years
Maximum | Land improvements and buildings
Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives (years)	40 years
Retail Properties | Post Heights [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1997
Retail Properties | Highlands of West Village [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2012
Phase I | Wholly Owned Properties - Residential | Colonial Village at Trussville
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1996
Phase I | Wholly Owned Properties - Residential | Colonial Grand at Bellevue
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1996
Phase I | Wholly Owned Properties - Residential | Post Addison Circle [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1998
Phase I | Wholly Owned Properties - Residential | Post Heights [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1998
Phase I | Wholly Owned Properties - Residential | Post Uptown Village [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1995
Phase I | Wholly Owned Properties - Residential | Post Worthington [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1993
Phase I | Wholly Owned Properties - Residential | Colonial Village at Grapevine
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1985
Phase I | Wholly Owned Properties - Residential | Post Midtown Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1999
Phase I | Wholly Owned Properties - Residential | Cityscape at Market Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase I | Wholly Owned Properties - Residential | Station Square at Cosner's Corner
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase I | Wholly Owned Properties - Residential | Post Carlyle Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2006
Phase I | Wholly Owned Properties - Residential | Post Rocky Point [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1994
Phase I | Wholly Owned Properties - Residential | Colonial Grand at OldTown Scottsdale [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1994
Phase I | Wholly Owned Properties - Residential | Westside Creek I & II
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1984
Phase I | Wholly Owned Properties - Residential | St Augustine
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1987
Phase I | Wholly Owned Properties - Residential | Post Brookhaven [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1989
Phase I | Wholly Owned Properties - Residential | Post Peachtree Hills [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1992
Phase I | Wholly Owned Properties - Residential | Lake Lanier Club [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1998
Phase I | Wholly Owned Properties - Residential | Highlands of West Village [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2006
Phase I | Wholly Owned Properties - Residential | The Denton III [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase I | Wholly Owned Properties - Residential | Colonial Grand at Trinity Commons [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2000
Phase I | Wholly Owned Properties - Residential | River's Walk [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase I | Retail Properties | Post Addison Circle [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1998
Phase I | Retail Properties | Post Worthington [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1993
Phase I | Retail Properties | Post Midtown Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1999
Phase I | Retail Properties | Post Carlyle Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2006
Phase I | Retail Properties | Post Rocky Point [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1994
Phase I | Retail Properties | Rise Condo Development [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1999
Phase I | Other Property [Member] | Post Addison Circle [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1998
Phase II | Wholly Owned Properties - Residential | Colonial Village at Trussville
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1997
Phase II | Wholly Owned Properties - Residential | Colonial Grand at Bellevue
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2015
Phase II | Wholly Owned Properties - Residential | Post Addison Circle [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2000
Phase II | Wholly Owned Properties - Residential | Post Heights [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1999
Phase II | Wholly Owned Properties - Residential | Post Uptown Village [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2000
Phase II | Wholly Owned Properties - Residential | Post Worthington [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2008
Phase II | Wholly Owned Properties - Residential | Colonial Village at Grapevine
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1986
Phase II | Wholly Owned Properties - Residential | Post Midtown Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase II | Wholly Owned Properties - Residential | Cityscape at Market Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2015
Phase II | Wholly Owned Properties - Residential | Station Square at Cosner's Corner
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2016
Phase II | Wholly Owned Properties - Residential | Post Carlyle Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase II | Wholly Owned Properties - Residential | Post Rocky Point [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1996
Phase II | Wholly Owned Properties - Residential | Colonial Grand at OldTown Scottsdale [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1995
Phase II | Wholly Owned Properties - Residential | Westside Creek I & II
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1986
Phase II | Wholly Owned Properties - Residential | St Augustine
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2008
Phase II | Wholly Owned Properties - Residential | Post Brookhaven [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1992
Phase II | Wholly Owned Properties - Residential | Post Peachtree Hills [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1994
Phase II | Wholly Owned Properties - Residential | Lake Lanier Club [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2001
Phase II | Wholly Owned Properties - Residential | Highlands of West Village [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2012
Phase II | Wholly Owned Properties - Residential | The Denton III [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2014
Phase II | Wholly Owned Properties - Residential | Colonial Grand at Trinity Commons [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2002
Phase II | Wholly Owned Properties - Residential | River's Walk [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2016
Phase II | Retail Properties | Post Addison Circle [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2000
Phase II | Retail Properties | Post Worthington [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2008
Phase II | Retail Properties | Post Midtown Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase II | Retail Properties | Post Carlyle Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2016
Phase II | Retail Properties | Post Rocky Point [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 1996
Phase II | Retail Properties | Rise Condo Development [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2013
Phase II | Other Property [Member] | Post Addison Circle [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2000
Phase III [Member] | Wholly Owned Properties - Residential | Post Heights [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2009
Phase III [Member] | Wholly Owned Properties - Residential | Post Peachtree Hills [Member]
Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Date of Construction	Dec. 31, 2009