Concentration of Credit Risk - Schedule of Concentration Risk (Details) - property	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Total Assets | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)		10.00%		10.00%
Revenue | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)		7.00%	12.00%
Senior housing triple-net
Concentration Risk [Line Items]
Number of properties disposed	64
Senior housing triple-net | Total Assets | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)		39.00%		39.00%
Senior housing triple-net | Revenue | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)		43.00%	60.00%