Summary of Significant Accounting Policies - Cash And Escrow Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 27,683	$ 37,189
Long-term restricted cash	24,268	22,710
Cash and escrow deposits - restricted, total	51,951	59,899
Real estate tax and property insurance escrows
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	18,177	21,603
Replacement reserve escrows
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	8,273	10,960
Resident deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	489	678
Other
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	744	3,948
Insurance deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Long-term restricted cash	14,370	12,364
CCRC escrows
Restricted Cash and Cash Equivalents Items [Line Items]
Long-term restricted cash	9,618	8,526
Debt service reserve
Restricted Cash and Cash Equivalents Items [Line Items]
Long-term restricted cash	$ 280	$ 1,820