Real Estate and Lending Activities - Summary of Status Update on Current Development Projects (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Business Acquisition [Line Items]
Commitment	$ 158,679
Costs Incurred as of March 31, 2018	35,122
Circle Health [Member] | Birmingham, England [Member]
Business Acquisition [Line Items]
Commitment	45,211
Costs Incurred as of March 31, 2018	$ 18,369
Estimated Completion Date	1Q 2019
Surgery Partners [Member] | Idaho Falls, ID [Member]
Business Acquisition [Line Items]
Commitment	$ 113,468
Costs Incurred as of March 31, 2018	$ 16,753
Estimated Completion Date	1Q 2020