Summary of Significant Accounting Policies - Leasing Costs and Revenue Recognition (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) community	Dec. 31, 2019 USD ($) community	Dec. 31, 2018 USD ($) community	Jan. 01, 2019 USD ($)
DEFERRED LEASING COSTS
Unamortized gross balance of deferred leasing costs	$ 44,506	$ 42,014
Accumulated amortization	$ 15,605	14,922
Weighted average amortization period for deferred leasing cost	7 years 7 months 6 days
Expected amortization expense for the five years
Expected amortization expense, 2021	$ 5,464
Expected amortization expense, 2022	4,468
Expected amortization expense, 2023	3,894
Expected amortization expense, 2024	3,403
Expected amortization expense, 2025	2,933
Expected amortization expense, thereafter	8,739
Operating lease, right-of-use asset	4,237	4,319		$ 4,507
Operating lease, liability	4,410	4,461		$ 4,507
Percentage rents earned	$ 2,144	$ 2,958	$ 8,443
Senior Living Communities | Five Star
Expected amortization expense for the five years
Number of communities managed | community	235	78	76