Summary of Significant Accounting Policies - Cash And Escrow Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 26,856	$ 27,683
Long-term restricted cash	34,614	24,268
Cash and escrow deposits - restricted, total	61,470	51,951
Real estate tax and property insurance escrows
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	16,299	18,177
Replacement reserve escrows
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	9,071	8,273
Resident deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	475	489
Other
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	1,011	744
Insurance deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Long-term restricted cash	23,692	14,370
CCRCs escrows
Restricted Cash and Cash Equivalents Items [Line Items]
Long-term restricted cash	10,641	9,618
Debt service reserve
Restricted Cash and Cash Equivalents Items [Line Items]
Long-term restricted cash	$ 281	$ 280