Organization - Additional Information (Detail)	Dec. 31, 2017 Community State Resident	Dec. 31, 2016 Community
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Senior housing communities operated by company	129
Number of states in which senior housing communities operated | State	23
Aggregate capacity of residents in company operated senior housing communities | Resident	16,500
Senior housing communities owned by company	83
Senior housing communities on lease by company	46	50