Real Estate Activities - Leasing Operations - Additional Information (Detail)	12 Months Ended
Dec. 31, 2018 Lease
Alecto Healthcare Services [Member]
Business Acquisition [Line Items]
Number of direct financing leases	2
Ernest [Member]
Business Acquisition [Line Items]
Number of direct financing leases	15
Prime Facilities [Member]
Business Acquisition [Line Items]
Number of direct financing leases	10

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration