Real Estate and Lending Activities - Loans - Additional Information (Detail) $ in Millions	Sep. 30, 2017 USD ($) Property Operator
Ernest Transaction and Other Acquisitions [Member]
Business Acquisition [Line Items]
Existing mortgage loans	$ 114.4
Mortgage Loans [Member] \| Steward [Member]
Business Acquisition [Line Items]
Number of Real Estate Properties \| Property	14
Number Of Operators \| Operator	4
Existing mortgage loans	$ 700.0

Total carrying amount of mortgage loans as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.6)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Name:	us-gaap_MortgageLoansOnRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant