Intangible Lease Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015
Intangible Assets And Liabilities [Line Items]
Total amortization expense	$ 1.7	$ 1.2
Income Properties Revenue [Member]
Intangible Assets And Liabilities [Line Items]
Amortization of lease liabilities in income properties	$ 1.7

The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration