Concentration of Credit Risk - Schedule of Concentration Risk (Details) - property	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Total Assets | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)			11.00%		17.00%
Revenue | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)	8.00%	12.00%	10.00%	12.00%
Senior housing triple-net
Concentration Risk [Line Items]
Number of properties classified as held for sale	3		3		64
Senior housing triple-net | Total Assets | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)			42.00%		69.00%
Senior housing triple-net | Revenue | Brookdale
Concentration Risk [Line Items]
Concentration risk (as a percent)	48.00%	60.00%	53.00%	59.00%