Summary of Significant Accounting Policies - Leasing Costs and Revenue Recognition (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) community	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
DEFERRED LEASING COSTS
Unamortized gross balance of deferred leasing costs	$ 42,014	$ 35,145
Accumulated amortization	$ 14,922	11,422
Weighted average amortization period for deferred leasing cost	13 years
Expected amortization expense for the five years
Expected amortization expense, 2020	$ 5,013
Expected amortization expense, 2021	4,292
Expected amortization expense, 2022	3,469
Expected amortization expense, 2023	2,944
Expected amortization expense, 2024	2,473
Expected amortization expense, thereafter	8,901
Percentage rents earned	$ 2,958	$ 8,443	$ 10,168
Senior Living Communities | Five Star
Expected amortization expense for the five years
Number of communities managed | community	78