Basis of Presentation and Significant Accounting Policies - Additional Information (Details)			12 Months Ended
	Jan. 01, 2018 USD ($)	Feb. 29, 2016	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Property Plant And Equipment [Line Items]
Minimum percentage of taxable income distributed to shareholders			90.00%
Federal income tax rate			35.00%
Decrease in deferred tax assets due to tax rate reduction			$ 405,000
Income tax expense			$ 5,177,000	$ 1,785,000	$ 2,566,000
Number of reportable segments | Segment			3
ASU 2016-02 [Member]
Property Plant And Equipment [Line Items]
Lease term, in months		12 months
ASU 2016-18 [Member]
Property Plant And Equipment [Line Items]
Increase in cash provided by used in operating activities continuing operations				3,000,000
Increase in cash provided by used in investing activities continuing operations				15,449,000	13,905,000
Subsequent Event [Member]
Property Plant And Equipment [Line Items]
Federal income tax rate	21.00%
Subsequent Event [Member] | ASU 2017-05 [Member] | RDF [Member] | 75 Howard [Member]
Property Plant And Equipment [Line Items]
Adjustment to investments in unconsolidated joint ventures	$ 7,086,000
Taxable REIT Subsidiaries [Member]
Property Plant And Equipment [Line Items]
Income tax expense			$ 5,758,000	780,000	2,545,000
Deferred income tax benefit			$ 922,000	$ 479,000	$ 1,186,000
Minimum
Property Plant And Equipment [Line Items]
Estimated useful lives of the assets, years			5
Maximum
Property Plant And Equipment [Line Items]
Estimated useful lives of the assets, years			40