Real Estate and Lending Activities - Summary of Status Update on Current Development Projects (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Business Acquisition [Line Items]
Commitment	$ 179,669
Costs Incurred as of September 30, 2018	59,796
Circle Health [Member] | Birmingham, England [Member]
Business Acquisition [Line Items]
Commitment	44,228
Costs Incurred as of September 30, 2018	$ 24,113
Estimated Rent Commencement Date	1Q 2019
Circle Health Rehabilitation [Member] | Birmingham, England [Member]
Business Acquisition [Line Items]
Commitment	$ 21,973
Costs Incurred as of September 30, 2018	$ 5,304
Estimated Rent Commencement Date	3Q 2019
Surgery Partners [Member] | Idaho Falls, ID [Member]
Business Acquisition [Line Items]
Commitment	$ 113,468
Costs Incurred as of September 30, 2018	$ 30,379
Estimated Rent Commencement Date	1Q 2020