Real Estate and Lending Activities - Concentrations of Credit Risk - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($) Investment	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) Investment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 Investment
Business Acquisition [Line Items]
Revenue from affiliates of total revenue	$ 224,756	$ 196,996	$ 597,759	$ 603,944
Total Gross Assets [Member] | Geographic Concentration [Member] | U.S. [Member]
Business Acquisition [Line Items]
Percentage of concentration risk			73.00%		80.00%
Total Gross Assets [Member] | Geographic Concentration [Member] | Europe [Member]
Business Acquisition [Line Items]
Percentage of concentration risk			20.00%		20.00%
Total Gross Assets [Member] | Geographic Concentration [Member] | Australia [Member]
Business Acquisition [Line Items]
Percentage of concentration risk			7.00%
Revenue [Member] | Customer Concentration Risk [Member] | General Acute Care Hospital and Healthcare System [Member]
Business Acquisition [Line Items]
Percentage of concentration risk			86.00%	86.00%
Revenue [Member] | Customer Concentration Risk [Member] | Rehabilitation Hospital with Covenant Health System [Member]
Business Acquisition [Line Items]
Percentage of concentration risk			10.00%	10.00%
Revenue [Member] | Customer Concentration Risk [Member] | Long-term Acute Care Hospital [Member]
Business Acquisition [Line Items]
Percentage of concentration risk			4.00%	4.00%
Revenue [Member] | Customer Concentration Risk [Member] | Steward and Prime [Member]
Business Acquisition [Line Items]
Maximum percentage of entity's revenue invested	4.00%		4.00%
Revenue [Member] | Credit Concentration Risk [Member] | Steward [Member]
Business Acquisition [Line Items]
Revenue from affiliates of total revenue			$ 265,100	$ 226,000
Revenue [Member] | Credit Concentration Risk [Member] | Prime [Member]
Business Acquisition [Line Items]
Revenue from affiliates of total revenue			$ 96,000	95,400
Revenue [Member] | Credit Concentration Risk [Member] | MEDIAN [Member]
Business Acquisition [Line Items]
Revenue from affiliates of total revenue				$ 99,900
Pro Forma [Member] | Total Gross Assets [Member] | Customer Concentration Risk [Member]
Business Acquisition [Line Items]
Number of investment in property | Investment	0		0		0
Maximum percentage of entity's assets invested on single property	3.00%		3.00%		4.00%