Real Estate and Lending Activities - Direct Financing Leases - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2019 Lease
Ernest [Member]
Direct Financing Lease Income [Line Items]
Number of direct financing leases	14
Prime Facilities [Member]
Direct Financing Lease Income [Line Items]
Number of direct financing leases	10
Alecto Healthcare Services [Member]
Direct Financing Lease Income [Line Items]
Number of direct financing leases	2