Real Estate and Loans Receivable - Summary of Status on Current Development Projects (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Commitment	$ 185,127
Costs Incurred as of 12/31/2017	47,695
Ernest [Member] | Flagstaff, Arizona [Member]
Business Acquisition [Line Items]
Commitment	28,067
Costs Incurred as of 12/31/2017	$ 21,794
Estimated Completion Date	1Q 2018
Circle [Member] | Birmingham, England [Member]
Business Acquisition [Line Items]
Commitment	$ 43,592
Costs Incurred as of 12/31/2017	$ 14,694
Estimated Completion Date	1Q 2019
Surgery Partners [Member] | Idaho Falls, ID [Member]
Business Acquisition [Line Items]
Commitment	$ 113,468
Costs Incurred as of 12/31/2017	$ 11,207
Estimated Completion Date	1Q 2020