Organization (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) community building investment apartment project shares	Dec. 31, 2018 USD ($) shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General partner ownership interest	96.60%	96.60%
Limited partner - ownership percentage	3.40%	3.40%
Operating Partnership units outstanding (in shares) | shares	2,301,653	2,305,389
Redemption value of operating partnership units outstanding | $	$ 692.5	$ 565.3
Number of apartment communities owned | community	250
Number of apartment units owned | apartment	60,570
Ownership interests, number of commercial buildings | building	1
Ownership interests, number of consolidated projects | project	5
Ownership Interests, number of unconsolidated projects | investment	2