Acquisitions, Dispositions and Other Significant Transactions - Additional Information (Details)	12 Months Ended				36 Months Ended
	Dec. 31, 2019 community	Dec. 31, 2018 joint_venture community	Dec. 31, 2017 community	Dec. 31, 2016 community	Dec. 31, 2018 community
Communities Disposed Of Through Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of		22	3	50	75
Communities Disposed Of Through Lease Terminations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of		89	105	7	201
Ownership Interests In Unconsolidated Ventures
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of unconsolidated ventures interest sold | joint_venture		7
Communities Disposed Of Through Sale And Lease Terminations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of					276
Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities expected to be sold	13
Communities Acquired Previously Leased Or Managed
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities acquired		6
Current Property Ownership Status
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities owned		344
Number of communities leased		343			343
Number of communities managed		18
Number of communities managed by third party		187			187