Fair Value of Financial Instruments (Details) - Fair Value, Inputs, Level 2	12 Months Ended
Dec. 31, 2017
Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Interest rate used to estimate fair value of mortgages and notes payable (in percents)	3.90%
Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Interest rate used to estimate fair value of mortgages and notes payable (in percents)	4.60%

Risk-free interest rate assumption used in valuing an instrument.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Period Type:	duration