Summary of Significant Accounting Policies - Leasing Costs and EPS (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) living_unit community	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Revenue Recognition
Percentage rents earned	$ 10,169	$ 10,062	$ 10,155
DEFERRED LEASING COSTS
Unamortized gross balance of deferred leasing costs	24,825	21,708
Accumulated amortization	6,898	$ 5,561
Deferred costs, leases under negotiation	$ 140
Weighted average amortization period for deferred leasing cost	8 years 6 months
Expected amortization expense for the five years
Expected amortization expense, 2017	$ 3,183
Expected amortization expense, 2018	2,835
Expected amortization expense, 2019	2,473
Expected amortization expense, 2020	2,030
Expected amortization expense, 2021	1,449
Expected amortization expense, thereafter	$ 5,817
Senior Living Communities | Five Star
Revenue Recognition
Number of properties acquired, referred to as managed properties | living_unit	68
Private senior living manager
Revenue Recognition
Number of properties acquired, referred to as managed properties | community	5